Microbiology Laboratory Report

1. Ascaris Lumbricoides – Male and Female

Ascaris Lumbricoides commonly known as the giant roundworm is a human parasite and is a causative agent of ascariasis. It belongs to the phylum Nematoda. An estimated 25% of people have ascariasis, which is prevalent in sub-tropic and tropical countries (Guy 1). The disease is quite common in regions with poor sanitation. Farmers who use human feces as fertilizer are also predisposed to the disease. Being an obligate parasite that is internal, it is prevalent in all human settlements. The eggs exhibit superior durability as they are resistant to various adverse conditions and can remain dormant for up to ten years in the soil. The worm protects itself from host enzymatic degradation by secreting a pepsin inhibitor. Moreover, it utilizes muscular activity to evade excretion. In its lifecycle, the larva traverses both the lymphatic and circulatory system via the heart, liver, and lungs. In very few cases, the worms migrate to the pancreas, brain, kidneys or  appendix.

Morphology

Ascaris Lumbricoides – Female

The width is 3-6 mm and the length is 20-49 cm. The anterior end has the vulva and makes up a third of the body length. At any given time, the uteri harbors 27 million eggs and 200, 000 eggs are laid daily. The unfertilized eggs are bigger with a width and length of 44 µm and 88-94 µm respectively. They are encased in a thin shell. Fertilized eggs have a width and length of 35-50 µm and 45-75 µm respectively. The fertilized eggs are encased in an outer shell that is thick. Decorticate eggs lack the thick mamillated layer (Guy 1).

Figure 1. Image of female Ascaris Lumbricoides (CDC, 1).

Ascaris Lumbricoides– Male

The diameter is 2-4 mm and the length is 15-31 cm. The posterior end has a ventral curve and the tail is bluntly pointed. Both male and female adults possess an anterior end with three lips.

Figure 2. Image of male Ascaris Lumbricoides (CDC, 1).

2. Stemonitis

Stemonitis species comprise elegant and distinct slime moulds. They belong to the phylum Myxomycota and colonize dead wood as well as leaves (Emberger 1). The sporangia are very slender and the length varies across species. The width of these slime moulds is 1-1.5 mm and the length is 2 cm. Stalks extend to the head form a support column, which is referred to as the columella. The spore mass is supported by a capillitum network. For Stemonitis axifera, sporangia are brown upon maturation. These sporangia develop in clusters with each cluster deriving support from the hypothallus (a cellophane base). These species colonize wood and have the capacity to rot entire logs at a rapid rate.

Figure 3. Image of Stermonitis axifera on a cut shrub of wood

The slime moulds have sporangia that resemble that of true fungi. The slime moulds are exemplified by Stermonitis sp.  They proliferate on wood, but unlike true fungi, Stermonitis do not produce hyphae, which penetrate and form an absorptive mass in the wood substrate. Instead, slime moulds produce plasmodia that have no cell walls. These plasmodia are protoplasm masses that are used for locomotion and engulf food particles in a fashion that is amoeboid.The plasmodia of slime molds creep above the surface and engulf fungal spores, bacteria, protozoa, organic matter, and plants. Thereafter, the plasmodia transform into sporangia (spore bearing structures). In the case of Stermonitis, the plasmodium transforms into clustered stalked masses of sporangia (Emberger 1).

In Stermonitis fusca, a young plasmodium has a diploid swarm cell. Its amoeboid plasmodial cells and planogametes have been found to be photophobic. In addition, the aphanoplasmodium emerges at a stage during plasmodial growth.In microculture, there is disintegration of the plasmodia, which give way to protoplasmic spherules (Benedict 355).

3. Saprolegina

Saprolegina belongs to the phylum Heterokontophyta. It is a water mould that is a necrotroph as well as a saprotroph. It feeds on fish waste and dead cells. They cause mycoses upon fungal infection. It can tolerate low temperatures below 3°C. Although it is found in fresh water, it can also proliferate in moist soil and brackish water. The fungus has long hyphae whose ends are rounded, and these also contain zoospores. The hyphae mature to a mycelium and the fungi coalesce to form white colonies. These white colonies turn grey upon contact with bacteria and debris to form a fibrous mass (Mayer 2).

The fungus has lifecycle that is diploid, which comprises both asexual and sexual reproduction. During the asexual stage, primary zoospores are released from a spore. Immediately, the zoospores encyst and germinate, and another secondary zoospore is released upon maturation. The second zoospore exhibits a longer life cycle and dispersal occurs at this stage. The released zoospores continue encysting and releasing new spores. This release cycle in Saprolegina is known as polyplanetism and continues until the secondary zoospores get a good substrate (Mayer 3).

Saprolegina infection

This fungus Saprolegina is a notable pathogen of fish and their eggs, especially trout and salmon. The fungus is prevalent in natural environments and affects damaged sites of live fish. Fibrous white and grey patches are formed upon infection of these damaged sites. The fungus also colonizes dead eggs, dead juveniles, and dead fish. Adult salmon in fresh water environments are highly susceptible because their scales get looser and their skin becomes less thick after occupation of the freshwater environment. The infection is exacerbated by stress and the numbers of infected fish that release the sores for subsequent infection (TDSBF 1).

The rate of disease infection is highest in regions where large numbers of fish occupy a small area. It occurs when a barrier prevents fish from migrating upstream or when the fish are stressed. It means that fish in rivers with too low water levels or downstream a waterfall in low water levels are highly susceptible.

4. Fucus male conceptacle

Fucus is commonly referred to as seaweed or kelp. It is a genus of brown macroalgae that is found exclusively in the marine environment and are members of the Phaeophyceae family. They have green chlorophylls that are masked by the fucoxanthin phytopigment. The seaweeds are diploid and gametes are formed after meiosis. Their reproductive organs are conceptacles and receptacles. Conceptacles are crypt like specialized structures where the production of gametes takes place. They are encased in the receptacles of plants. Some species are dioecious and some are monoecious. The monoecious Fucus species contain both sexes in conceptacles, while the others have the sexes in separate concepatcles.

Conceptacles for male reproductive organs have a lining of antheridiophores. The antheridiophores are branched, and the branches bear terminal inflated antheridia. These antheridia are meiosis sites and produce male biflagellated gametes known as antherozoids. Both female and male gametes are released in the water in the course of rising tide alongside female eggs, which release fucoserraten, a volatile potent hydrocarbon. Fucoserraten serves as an attracting agent for the male antherozoids. After fertilization, the eggs settle on the sediment where they germinate into diploid thallus (Davidson, 1995).

Fucus is also important medicinal seaweed and these species exhibit a high antioxidant activity. They are used as dietary supplements in the food industry. The brown algae are also very rich in iodine and also serve as a remedy for thyroid problems. They are immune boosters, reduce cholesterol, and prevent breast cancer.

5. Coprinus mushroom

Coprinus mushrooms have few species and the most well-known species is Coprinus comatus (commonly known as shaggy mane). They belong to the family Agaricaceae and are Basidiomycetes. In the temperate regions of the world, the mushroom appears during late summer (Osathaphant 1). The production cycle is short (1-2 months). The mushroom is widely cultivated in Thailand and North America and can adapt to both outdoor and indoor substrates. The fruiting body is 15 cm high and has a thickness of 5 cm. The mushrooms assume a vertical oblong shape, and bear ascending scales. During the early stages the fruiting, body is dingy brown but changes to white during maturation. The gills are broad, long, pale/white, crowded, and free or slightly attached to the stem. The stems have a length of 15 cm and thickness of 1-2 cm. These stems have a bulbous base, are hollow and possess a membranous movable ring. This ring detaches from the margin with the enlargement of the mushrooms.

Figure 4. Image of Coprinus comatus

Coprinus mushrooms comprise three genera: Parasola, Coprinopsis, and Coprinellus. Parasola has tiny species that are umbrella like. They lack a universal veil, granules, patches, and scales. The most well-known species is Parasola plicatilis  (Kuo 1). It is very small with a thickness of 35 mm. Their cap is initially ovoid and becomes bell-shaped/convex and is flat during maturity. In the young stages, it is yellowish or orange-brown and is grey upon maturity. The most distinctive feature of the species is the spores which are large, angular, and fat. They also contain a pore that is eccentric. The flesh is insubstantial and white. The gills are initially white and turn dark-grey during growth and are eventually black upon maturity. These gills are free or close to the stem (Kuo 1).

Figure 5. Image of Parasola plicatilis

Coprinellus and Coprinopsis species are similar, but can be separated via microscopic analysis. Coprinopsis species have noticeable veils. Coprinellus species have an ozonium, which is a fibroid orange mat at the base of the stem. These species also have granules that are mica-like at the surface of the cap. The species are partially deliquescent.

6. . Trypanosoma brucei gambiense

The parasite is a protozoan hemoflagellate. Trypanosoma brucei gambiense is the causative agent for Human African Trypanosomiasis (HAT). This disease is a serious health concern in Sub-Saharan Africa. This organism causes West African sleeping sickness and should be distinguished from Trypanosoma brucei rhodesiense, which cause East African sleeping sickness. The parasites exist as trypomastigotes in human hosts. With respect to morphology, the parasite is spindle shaped and elongated, and the posterior end is blunt and the anterior end is pointed (CDC 1).

Figure 6. Image of Trypanosoma brucei gambiense

Life cycle

Tsetse flies (from the genus Glossina) are the vectors for trypanosomes. And the infected tsetse flies inject the trypanosomes into the skin tissue. Tsetse flies inject the metacyclic trypomastigotes. The parasites enter the systemic circulation via the lymphatic system. The metacyclic trypomastigotes transform into trypomastigotes in the bloodstream. The parasites are transported to other body sites by the blood fluids, and they continue to replicate via binary fission. A tsetse fly is infected with the trypomastigotes by ingesting infected blood from a mammalian host. The parasites mature to procyclic trypomastigotes in the midgut and replicate via binary fission. Upon leaving the midgut, they mature into epimastigotes. These epimastigotes move to the salivary glands where they continue to replicate via binary fission (CDC 1). The fly cycle of tryapanasomes takes 3 weeks. Humans remain the major reservoirs for T.b. gambiense.

Clinical symptoms and pathology

The biting site exhibits local inflammation. The acute Gambian trypanosomiasis disease lasts for a year. The symptoms include muscle pains, rash, joint pains, headache, and irregular fever. There is enlargement of the lymph nodes and those in the postcervical region (Winterbottom’s sign). Thereafter, the disease progresses to the chronic state and is characterized by changes in the central nervous system. There is the development of meningomyelitis and diffuse meningoencephalitis. There is prominent evidence of nervous impairment, and this is the stage of terminal sleeping (CDC 1). Death will ensue from Gambian Trypanosomiasis or intercurrent infections.

Prevention is via effective control of tsetse flies. Chemoprophylaxis is conducted using pentamidine. Laboratory diagnosis is via microscopic examination and animal inoculation. Microscopic examination is conducted on spinal/bone marrow fluid, lymph, and blood (CDC 1).

7. Penicillium

Penicillium is an ascomycete. It is an important fungus in the pharmaceutical and food industry. These fungi produce penicillin, an important antibiotic. Penicillium is derived from the word penicillus, which means ‘brush.’ The secondary metabolites produced by Penicillium species have proven revolutionary in the treatment of infectious diseases like gonnorhoea and pneumonia. The appearance of fruiting structures is brush-like. The heads are brush like and the stalks are referred to as conidiophores as they branch near the tip. These branchlets form phialides that are spore producing cells at the tip. The spores are referred to as conidia or phialsopores. The conidia of Penicillium digitatum and Penicillium italicus have a green or blue pigmentation. They give the color to blue cheese. Penicillium colonies proliferate rapidly and are filamentous and flat. Their texture is cottony, velvety, or woolly. They are initially white, and with maturation, they become pinkish, olive-gray, gray-green, or blue-green (University of Adelaide 1).

Figure 7. Image of Penicillium sp.

Penicilium chrysogenum also referred to as Penicillium notatum, Penicillium purpurogenum, Penicillium citrinum, Penicillium frequentans, Penicillium janthinellum, Penicillium purpurogenum, and Penicillium marneffei are considered common species. The molds proliferate in dark and damp sites. They are dominant in soils found in the temperate regions, and the spores are dispersed easily in the atmosphere. The molds are most prevalent in decaying vegetation, forests, soil, and compost in forests of the temperate zones, cultivated land, as well as the grasslands (University of Adelaide 1).

Clinical Significance

Penicillium species are contaminants and produce potent mycotoxins. They are significant food contaminants. Some opportunistic infections arise in humans, especially after insertion of prosthetic valves, and these include: endocarditis, otomycosis, and mycotic keratitis. P. marneffei have been reported in patients with AIDS (University of Adelaide 1).

8. Peridinium

Peridinium is a dinoflagellate that belongs to the kingdom Chromista. They were initially thought to be of ancient eukaryotic lineages. Recent evidence suggests that they are related to apicomplexan sporozoans and ciliates. They posses thick plates that are armored, ornamented, and lobed. Peridinium limbatum has distinct horns. The sutures are conspicuous, and at the cell’s median, there is the cingulum. The shape of the cells is flat or oval. The ventral surface is concave, and the dorsal surface is convex. There are above 30 species of Peridinium, with most of them being photosynthetic. The non-photosynthetic species are osmotrophic or phagotrophic.

Figure 8.  Image of Perinidium

These species are found in the fresh water as well as planktonic marine habitats all over the world. The photosynthetic species produce significant blooms commonly referred to as “red tides.” Some blooms are linked to fish mortality and nuisance odors (Parker 21).

9. Taenia Pisiformis Gravid

Taenia Pisiformis Gravid belongs to the phylum Platyhelminthes and is commonly known as the “dog tapeworm” because dogs act as definitive hosts; rabbits or rodents and some largomorphs act as intermediate hosts. The tapeworm uses its scolex to adhere to the canine’s digestive tract and depends wholly on the nutrients from its host. Growth of new proglottids starts at the scolex near the base and progress downwards as the worm grows longer. The scolex is cube shaped and bears a sucker at the corner of each end and a rostellum at the top, which is surrounded by hooks arranged in two layers. The rostellum expands and contracts, and this enables the tapeworm to bury deep inside the gut lining of the canine to protect the scolex, neck, and the preceding segments. The tapeworm has excretory longitudinal canals that open through a lateral canal in the last proglottid. The mature proglottid has a single gonopore with openings for both the female and male gonads. The vagina expands into a seminal receptacle where the eggs are formed. Gravid proglottids enclose a uterus full of shelled eggs. The male canal consists of numerous testes that drain into a sperm duct (Parker 30).

The life cycle of Taenia Pisiformis starts with the gravid proglottids being defecated to the outside by the definitive host, a dog. The proglottids remain dormant in the vegetation until they are swallowed by rodents or rabbits, the intermediate hosts, which, in turn, are consumed by a dog, the main host. The egg hatches into an oncosphere and buries into the mesenteric veins and finally into the liver where it develops a tough exterior tegument and a mini scolex inside it. The cycle is completed with the dog feasting on the remains of the infected rodent and the proglottids attach to the tract and begin growing to start a new life cycle.

Figure 9. Taenia Pisiformis Gravid

10. Amoeba Proteus

Amoeba Proteus belongs to the kingdom Protozoa and the phylum Rhizopoda. It is characterized by being single-celled organisms and having body extensions known as pseudopodia, which are used for locomotion and nutrition. Its habitat different environments, which include soil, water, and mud, but some are parasitic like the amoeba proteus, which inhabits the fresh water. It was named after “Proteus,” the Greek god, who could change his shape. Its main diet consists of planktons and diatoms (Milwaukee 46)

The amoeba is single celled and contains a single nucleus with peripheral granules and a contractile vacuole where food is stored and digested, a process known as phagocytosis. The vacuole also serves the function of osmoregulation through exocytosis,  i.e expulsion of water to the outside. It has no defined shape as it shape shifts with the movement of its pseudopodia during motion. The cytoplasm has pyramid shaped crystals with scattered nucleolar material. The surface of the plasma membrane is covered with filaments and is impenetrable due to tightly packed helical shaped glycostyles with an estimated total thickness of 520 µm. Reproduction follows asexual means and is through mitosis and cytokinesis. As a protective measure, the amoeba forms a tough protective membrane to become a microbial cyst. It will remain dormant until the conditions become more favorable (Parker 10).

Figure 10. Amoeba Proteus

11. Paramecium

Paramecium tetraurelia is a single celled protozoan with cilia on its cell surface. It belongs to the class of  Apicomplexans, which also includes Plasmodium falciparum. They are found in the warm stagnant freshwater (Milwaukee 27). The cell has two nuclei: the micronucleus and the germinal nucleus that is responsible for transmission of genetic information, and the macronucleus or somatic nucleus that is responsible for the expression of this information. The paramecium reproduces through sexual and asexual or vegetative means, and a new somatic nucleus is developed from the genetic material in the germinal nucleus and both emanate from the zygote nucleus.

The life cycle of the paramecium starts with fission, which is the splitting of the cell along the middle into two, while the macronucleus divides into two identical parts with each going to a separate daughter cell. The sexual cycle involves two cycles: conjugation, which involves the fusion of two different strains into one; the micronuclei divide meoitically into four haploid micronuclei, all but one divide mitotically, and the resultant micronuclei are paired in each paramecium. The macronucleus disintegrates to form a new macronucleus from the resultant micronuclei, which then is fused. The second cycle is autogamy, which is a process of meiosis triggered by lack of food and happens in unpaired paramecium (Milwaukee 34)

12. Diatoms

These are unicellular organisms that belong to the kingdom Protista, phylum Chryosophyta, class Bacillariophyceae, and their main characteristic is that the diatoms living substance is held in shells made of cilica that they secrete. They are hydrophilic and are found in freshwater, moist soil, saltwater, brackish water, and moist plant surfaces. They are usually yellowish or brownish in color and are the main constituent of planktons, which form a very important food source for many marine fishes and mammals. They are believed to be about forty thousand recognized species. They are mainly autotrophic, but there are species that are heterotrophic and symbiotic. The diatoms have opening in its shells used to access the environment. They carry chlorophyll c and the carotenoid pigment fucoxanthin in their plastids. They reproduce asexually, which is mitotic, but in other conditions, they can reproduce sexually through meiotic cell division.

The marine diatoms help in the formation of diatomite used in explosives. The shell of the diatoms is not able to decay and falls to the bottom to accumulate to form diatomaceous material and when compact and chalky it forms diatomite. Diatoms are also responsible for the formation of limestone and the crude oil deposits.

13. Spirogyra

They are a familiar sight; the floating green algae found in the stagnant or slowly moving fresh water, especially rich in calcium where they become encrusted and eventually fossilized. They are unicellular and belong to the phylum Chlorophyta, class Charophyceae with a complex branched thallus. The filament is an adaptation that helps in osmoregulation chloroplast forms a spiral ribbon across the cell. The cells are symmetrical and geometric in shape; the mobile cells have two flagella at right angle to the top. The cell wall is made of cellulose with other polysaccharides and proteins (Milwaukee 25).

Sexual reproduction occurs through formation of a zygospore and zygotic meiosis. Tubular structures will develop from the two cells of two neighboring filaments. The tubes merge and form a pathway between each cell and the partner. The chloroplasts become less visible. The cytoplasm pulls out of the cell wall to form a rounded structure, the cytoplsmic contents contain the genetic code or gametes. The gamete of one filament is transferred and fuses with the gamete of the other cell forming a zygote; the cycle starts with mitosis where the nuclear envelope disintegrates, the mitotic spindle is present and phragmoplast aids in the development of the cell. The zygote will then develop a tough protective covering that becomes a spore. The spore is capable of remaining dormant until favorable conditions suffice, and when this happens the wall is shed off and a new spirogyra filament will start to grow.

14. . Physarum Plasmodium

It belongs to phylum apicomplexans, which are intracellular parasites and thrive and replicate in the vacuole of the host cell (Parker 35).

It possesses a unique structure; an apicoplast similar to a chloroplast and this ensures its survival from the host’s defenses. The parasite’s exterior is surrounded by a pellicle formed by the plasma membrane and the internal membrane complex. It also has a cluster of organelles; the apical polar ring, rhoptries, micronemes, and conoids to form the apical complex, their main characteristic. Rhoptries and micronemes are secretor organelles and serve in the function of mobility, formation of parasitophorous vacuole, host cell invasion roe, and adhesion. They rapidly replicate once in a host and are haploid for the most part, but differentiate to invade different tissues. Gametes could undergo male to female fusion to form a diploid zygote and back to a haploid organism. This enables the parasite to infect the vector agent that transmits it to the intended host organism.

A physarum slime mold is a large cell with many nuclei and is formed when the organism is facing unfavorable conditions. The cells are served by a rich network of veins and are involved in cytoplasmic streaming and movement. The veins are unique as they change according to the environmental condition being faced. The motion begins with the front edged veins forming a bulbous network while the back forms a skeleton – like section comprising the major vessels. Physarum has been observed to be chemotactic and thermotactic, that means it responds to both chemical signals and temperature gradients.

15. Rhizopus Sporangia

It is the most common known fungus also known as the bread mould (Gliddon 35). Rhizopus sporangia belong to a group of plants known as saprophytes and thrive in moist food, while some are weak facultative parasites and grow on plants causing infections when in transit. The structure of the fungal thallus, called the mycelium, is made up of long tubular filaments, which are of three types: stolons, rhizoids, and sporangiphores. The stolons are horizontally branched hyphae present on the surface and are stout in nature and grow at a rapid rate. The rhizoids develop from the lower surface of the stolon and provide anchorage. The other function is to absorb nutrients and also produce digestive enzymes like the amylases. The sporangiophores are located at the upper surface of the stolons and are unbranched hypha, which are in groups of two to five. The hypha is a filament that lacks septa and is transparent, tubular, and coenocytic. The cell wall is made of chitin and has dense protoplasm with many vacuoles, haploid nuclei, and other cell organelles. Food is stored in form of glycogen and oil globules.

There is sexual and asexual reproduction. In the vegetative cycle, the mycelium fragments and the newly formed mycelium can start thriving independently by producing rhizoids. The asexual cycle begins with sporangiospores and the formation of chlamydospores. Sporangiospore

Sporangiospore formation starts when the organism encounters favorable conditions, the sporangiophores swell at the tip to form sporangia with nucleated and a vacuolated region known as sporoplasm and columelloplasm respectively. The sporangia are single layered and number between two and ten. The spores are spread by wind and germinate in favorable environment to start the mycelium cycle.

Chlamydospore formation is a phenomenon that occurs in older stolons when the plant is facing unfavorable environment. Protoplasmic accumulation forms a thick wall around the spore transforming it to a multinucleated chlamydospore. Sexual reproduction occurs with the stolons transforming into sexual hyphae known as zygophores, and the fusion of two gametangia where all entire cell contents are exchanged to form diploid structure known as a zygospore. The zygospore will then germinate when the right conditions suffice.

Figure 15. Rhizopus Sporangia

16. Saccharomyces (Budding Cells yeast)

Commonly known as the “baker’s yeast”, Saccharomyces means “sugar fungus” with sugar as its main source of nutrients. S. cerevisiae is found growing wild on most fruits. The cell wall is composed of chitin and lacks peptidoglycan and the lipids are ester linked (Gliddon 35)

Saccharomyces cerevisiae has the following morphological adaptations. Food is degraded via both anaerobic and aerobic fermentation; hence their ability to survive in oxygen deficient environments. They also reproduce via both asexual and sexual means. This enables them to tolerate many different environments. Saccharomyces cerevisiae uses glucose as its energy source.

It has two distinctive characteristics: a round yeast- like form, which propagates by budding, and a filamentous form. In the nutrient rich environments, S. cerevisiae separates into two different spherical cells. On the contrary, in less favorable conditions, the cells become emaciated and square, and the resultant daughter buds remains attached and connected with the parent organism, the yeast goes through a dimorphic transition.

Saccharomyces cerevisiae exhibits two forms of reproduction in its life cycle. The asexual cycle starts with haploid yeast undergoing cell mitosis to subsequently produce more haploid yeasts. The new haploid yeasts from each strain fuse together and become one cell.

This is followed by the nuclei fusion from both cells to form a zygote. The zygote goes through mitosis called budding to replicate four more zygotes or meiosis to form an ascus, which will divide into four ascospores. These new zygotes undergo germination and develop to haploid yeast. Saccharomyces cerevisiae is responsible for ethanol production in baking powder and alcoholic drinks.

Figure 16. Saccharomyces (Budding Cells yeast)

17. Volvox

It belongs to the phylum Chlorophyta or the green algae (Reine 20). The cells are characterized by two whip-like flagella. They exist in colonies and are connected to each other by thin strands of cytoplasm to enable them move as a group of algae. They also have individual small red eye spots. The eyespots in the northern region are more developed as the algae are phototropic. They can be found in the eutrophic environments. The two most common species are Volvox aureus, which is smaller in size and has less individual cells, and Volvox globator, which is egg-shaped and larger in size and can be seen by the naked eye.

Figure 17. Volvox

Reproduction is both sexual and asexual. In the volvox, most colonies have “daughter colonies” replicated from the cells at the centre of the colony and serve as the gonads. These cells undergo division to form new algae. Sexual reproduction occurs through special germ cells. The male or sperm cells are formed by division, while the female germ cells enlarge to form an ovum. The sperm cells will swim to look for the ova. Fertilization occurs to produce a zygote, which, in turn, produces a tough protective layer. The zygotes of V. globator are star-shaped while the V. aureus have a smooth surface. They also have a parasitic rotifer that lives within and feeds on the cells.

18. Oedogonium

It belongs to unbranched filamentous green algae that belongs to the phylum Chlorophyta, order Oedogoniales, family Oedogoniaceae. Oedogonium have a preference for soft water abundant in humic compounds and iron. The main characteristic is the distinctive rings seen in the filament, which are a result of cell division. The cells are round-shaped and contain dense chloroplasts with several pyrenoids. The species are distinguished by cell variation, size of vegetative cells, shape of oogonia, location of antheridia, and the pattern variation in the zygote wall (Gliddon 15)

They reproduce sexually and vegetatively. The female cell is bigger in size compared to the male, which is attached to it. Zoospores are formed when the bulbous cells are transformed through vegetative reproduction. They are motile due to a ring of cilia on their cell surface and possess a hold fast disc which grows into a filament. The filaments vary in size. Some zoospores have a terminal cell called calyptra. Once the zoospores are released, they are on the move and will settle on a suitable surface. The attachment organ develops an attachment and the filament starts to grow.In sexual reproduction, oogonia are produced. They contain a single large non-flagellate egg cell and antheridia where the sperm is located. The sperm has multiple flagella. Some species are capable of self-fertilization and are described as monoecious, and the dioecious species require two filaments for fertilization to occur. The filaments are usually attacked by parasites such as aquatic fungi called chytrids and a dinoflagellate, Stylodinium. It is attacked by the amoeboid stages and the all the cell contents are consumed.

Figure18. Oedogonium

19. Stentor

Stentor is the largest species of protozoans found in water. Protozoa are unicellular organisms and belong to the kingdom Protista. They are present in the freshwater ponds and are larger in size compared to many multi- cellular fresh water organisms and prey on some of them. The single cell has a macronucleus in the form a string of beads and performs all the essential cell functions; reproduction, nutrition, digestion, excretion and respiration. They are visible as long trumpet shaped organisms on a microscope but changes to an oval in shape with a narrow posterior when in motion and contacts to a protoplasmic blob when distressed. The opening of the trumpet is surrounded by a crown of cilia that vibrate to produce currents drawing floating particles of food into the gullet.

Stentor has amazing regeneration ability and can regenerate a new complete organism from a small fragment. They also have a contractile vacuole, which performs the function of osmoregulation. They have a variety of colors: green, blue, and other colored species. An interesting fact is that they have a symbiotic relationship with the green microscopic algae that it ingests to give it a green color. The algae using photosynthesis and converts the Stentor’s wastes to nutrients that it utilizes.

Figure 19. Stentor

20. Polysophonia Sporophyte

Polysophonia comprise more than one hundred and fifty different species. The main characteristics are: an erect thallus with radial branching and are usually reddish-brown in color. Polysiphonous construction is typical and involves apical cells that are derived from the proximal segments which mature to axial cells upon elongation. These subsequent pericentral cells are of the same span and they surround the central axial cell forming one “tier.” The pericentral cells in each tier can be 4-24.

There are pores in between neighboring cells that fir plug caps or plugs, which give support to the thallus, it is known as a pit connection (Reine 34). The primary pit connections are formed in between axial cells and pericentral cells during cell division while the secondary pit connections are formed in between pericentral cells. Replicating cells occur in large numbers at the apical region with the newly formed branching to the left and the older ones forming a strip towards the right. The primary axis is the main structure where growth of the alga happens during the course of its life, with secondary, exogenous and endogenous branches growing from it. The branches are arranged in multiple planes.

21. Vorticella

They are protozoans that belong to the genus Vorticella and usually live independently; thought they can be found in colonies. These are not true colonies because they retain their individuality even within the colony, and the individual can leave at any time. They are found in both freshwater and seawater environments where they get plenty of bacteria, which are their source of food. They are found attached to plant detritus, crustaceans, rocks and algae. Young vorticella are usually found free swimming with the adults using the filamentous organelle, a contractile stalk known as spasmoneme attaching to substrates. If the stalk gets detached due to disturbance, search for food or new location they become free swimming. The spasmoneme is made of three cellular membranes, an extracellular matrix, and an outer sheath. When the stalks contract it, the organism coils, and this is an adaptation against environmental hazards and also assist in capturing food  (Gliddon 30).

They possess cilia, which are concentrated around the mouth and are used to direct food towards it. Temporary, cilia are formed around the body when the organism is in motion and once anchored, the cilia disappear. Reproduction is through binary fission where two new organisms are formed from the original splitting. They also undergo sexual reproduction.

Figure 21. Vorticella

22. Oscillatoria/ Cyanobacteria

These are the blue-green algae common in freshwater habitats (Reine 43). They are often attached to submerged plants, rock surfaces, or as loose floating mats. They are more common in nutrient rich wetlands and have been responsible for clogging irrigation canals during blooms. They have unbranched filaments with the characteristic mucilaginous sheaths around the axis, which are formed during dessication or hypersalinity. They do not have a true sheath. The trichome is motile and made up of disc shaped cells in the trichome and is not separated by deep constrictions. Sometimes the cells contain large granules. They are known for rhythmic oscillating motion, which is designed to keep the filaments away from waste matter. They reproduce by fragmentation where dead concave cells separate sections of the hormogonia or filament. Blue green algae are photosynthetic and they encounter optimal conditions which include high phosphorous and nitrogen level, lack of water disturbance they replicate rapidly and form a colony; although, they can exist as single cells. Oscillatoria species differ in the thickness of the filament and morphology.During blooming, they infect water sources for humans and other animals and exposure to its toxicity occurs through inhalation, ingestion, or dermal contact which will lead to allergic reactions and can result in a fatality in high exposure cases.

Figure. 22. Oscillatoria/ Cyanobacteria

23. Aspergillus Conidiophores

These are fungi of the phylum Ascomycota and the genus Aspergillus, which has over one hundred species and about twenty are agents of opportunistic infections. Some common species are Aspergillus terreus, Aspergillus versicolor, Aspergillus nidulans Aspergillus fumigates, Aspergillus nidulans Aspergillus flavus, Aspergillus niger, Aspergillus ustus Aspergillus clavatus, Aspergillus glaucus group, Aspergillus oryzae, and Aspergillus versicolor. They are filamentous and found in abundance in many environments.

Aspergillus species are more common and widespread and can be isolated from soil and plant debris. The morphology is characterized by hyphae, which are septate and hyaline. The conidophores are formed in basal foot cells on the supporting hyphae and ends in the vesicle at the tip. The foot cell is wider than the filament and loses the protoplasm when the spores mature. At the end of the cross walls or the non-septate stalk, there is an engorged vesicle that bears little stalks known as the sterigmata. This is where the mature spores are contained. The conidiophore varies from one species to another and is the key difference that distinguishes it from Penicilium species. Phialides cover the vesicle surface and are attached directly or via a metula (supporting cell). The phialides are round shaped and are two to five µm in diameter, forming radial rings (Gliddon 50).

Aspergillus niger is the most common nuisance mold and is related to opportunistic infection.  It prefers relatively warm climates. Aspergillus mold is useful in making alcohol due to is antibacterial and antifungal properties and is widely used in the production of different wines in Japan, such as sake, which a Japanese wine is made from rice.

Figure 23. Aspergillus Conidiophores

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