Saccharomyces

Class: Acromycetes

Order: Endomycetales

Family: Saccharomycetaeceae

Genus: Saccharomyces

Saccharomyces is saprophytic fungi (Yeast) found growing abundantly in sugary substance such as fruits, syrups, jams, nectar, honey, toddy etc. it is uni-cellular but sometimes the cell may remain attached giving the appearance of a pseudo mycelium. the cells are small oval or spherical in shape and grow as white or creamy colonies on the surface of solid nutrient media.

Each cell has a definite two layered cell wall made up of fungal cellulose with the chitin. The cell wall encloses the protoplasm which can be differentiated into outer ectoplasm and the inner endoplasm. The cell contains a large centroplasm consists of a single large nucleus, sub-cellular organelles like endoplasmic reticulum, ribosome, mitochondria, and reserved food material in the form of glycogen, volutin granules and oil globules.

REPRODUCTION

Saccharomyces reproduce by budding or fusion or by sexual reproduction.

BUDDING

It is the most common type of reproduction in which the parent cell gives rise to a small bud- like out growth. The nucleus of the parent cell divides in to two and one daughter nucleus along with cytoplasm enters the bud. The bud grows in size and may get a pinched-off from the mother cell or may remain attached to it intern forming bud, there by giving rise to pseudo mycelium.

SEXUAL REPRODUCTION
It is of isogamous type where two vegetative cells behave as gemates and put out small protuberances, which meats and forms conjugation tubes. The nuclei of the two gametes fuse along with cytoplasm and form a zygote which develops in to ascus. The diploid nucleus of the ascus under goes mitosis to form 4-8 ascospores which when release develop into new yeast cell.

Posted in: Microbiology

Aspergillus

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Class: Acromycetes

Order: Aspergillales

Family: Aspregillaceae

Genus: Aspergillus

Aspergillus is a wide spread fungus generally saprophytic and growing stale bread , fruits, vegetables, jams, jellies, foot wear etc. a few species of Aspergillus are parasitic causing lung disease (aspergillosis) and ear infection (outomycosis).

The mycelium consists of a hyaline branched, septate and multi nucleated hyphae. Most of the mycelium grows above the substratum. Some hyphae grow deep into the substratum and halt in the distribution of nutrient and encouraged.

REPRODUCTION

ASEXUAL REPRODUCTION

Asexual reproduction

From the vegetative mycelium many un-branched erect, fertile hyphae called conidiophores arise from thick-walled cells called foot cells. These conidiophores form a swollen dawn shaped vesicles at the tips. The vesicles produce bottle shaped structure called sterigmata, which produces chains of conidia at their tips in basipital sub sessions. The sterigmata are multi nucleated and maybe found in two layers in some spices. The asexual spore called conidia are small , unicellular ,spherical structure with a double layer wall. The outer layer is called epispore/ exime, which is spiny and inner layer called the endospores/ intine. The conidial wall is pigmented with shapes of black, blue, green, yellow etc. depending upon the species. The conidia germinate by the production of germ tube and develop into new hyphae. The conidia are light weighted and carried by a wind.

SEXUAL REPRODUCTION

Sexual reproduction

It is by means of gametengial contact between the male antheridium and female ascogonium, which maybe produced on the same or different hyphae. Fertilization results in the formation of fruiting body called ascocarps, cleistothecium , which encloses a number of asci, each containing 8 ascospores, which when liberated germinates to give rise to a new mycelium.

ECONOMIC IMPORTANCE

A.niger also called the black mold is used in the industrial production of citric acid and glycolic acid.

A.flavus is known to produce a mycotoxin called aflatoxin.

Many species are important in food spoilage and some are known to cause disease.

Posted in: Microbiology

Penicillium

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Class: Acromycetes

Order: Aspergillales

Family: Aspregillaceae

Genus: Penicillium

Penicillium is commonly called blue mold. It is a saprophytic found growing in decaying fruits and vegetables, especially citrus fruits-like orange and lemon. The mycelium consists of pale hyaline brightly hyphae which generally grow superficially on the substratum, the hyphae are septate branched and uni- nucleated.

REPRODUCTION

ASEXUAL REPRODUCTION

It is for the formation of conidia on special branch called conidiopores. The conidiophores is the long, slender septate grows right from the vegetative hyphae . They maybe branched or unbranched. The ultimate branches of the cornidiophore are called matulate. The metulate produce bottle shaped cells called sterigmata or phialides. The conidia are born in chains of basipital successions at the tip of each stigma. The terminal part of the cornidiophore has a brush or broom-like appearance knows as penicillus hence the name penicillium. The conidia are blue green, olive green or grey depending upon the species. They are globose in shape, uni-nucleate and has a smooth wall. They germinate and give rise to a new mycelium

SEXUAL REPRODUCTION

It is by means of gametangial contact between the male antheridium and female ascogonium which maybe produced on the same or different hyphae. Fertilization results in the formation of fruiting bodies called ascocarps, cleisthothecium which encloses the number of asci. Each containing 8 ascospores which when liberated germinates to give rise to a new mycelium.

ECONOMIC IMPORTANCE

The genus penicillium is of great ecomomic importance .concidering the dis advantage of fungus first. It causes great demage of furniture .fabrics etc. .The profuse growth growth of mycelium on the windows ,furniture etc, forms a blue coating .oe of the greatest demages iscaused to the fruits and vegetables for example. P.digitatum and P.expansum cause the decay of sitrus fruits . the latter spices are causing the decay of apples. Some of the spices are causing animat and human diease. For example. Pencillosis of lungs. However these can be controlled by careful hanling og material. Keeping them under restricted air supply , low temperature and dry condition

Posted in: Microbiology

Rhizopus

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Class: Zygomycetes

Order: Mucorales

Family: Mucoraceae

Genus: Rhizopus

Rhizopus is commonly called bread molds. It is a saprophytic fungus found growing on bread, jam, pickles, decaying vegetables and fruits etc. the plant body consists of white cottony mycelium growing over the substratum. The young mycelium consists of long aseptate coenocytic hyphae. The older mycelium has three types of hyphae

1. Stolons : they are staut cylindrical creeping hyphae . They are differentiated in to nodes and inter nodes.

2. Rhizoidal hyphae: it produces at the node of the stolon .they are highly branched and penetrated into substratum .they provide courage and absorb food.

3. Sporangiopore: they are Arial staut hyphae which arise from substratum from the time of asexual reproduction. They develop from the node in clusters. Initially the hyphae have the cell wall made up of fugal cellulose. It encloses the cytoplasm. Hyphae are asepetate coenocytic, small vacuoles, oil droplets and glycogens are distributed in the cytoplasm.

ASEXUAL REPRODUCTION

It is by the formation of spore. The sporangiopore are short staut and arise at the node of stolon in clusters. A single sporangium is developed at the apex of each sporangiopore. Each sporangium is spherical in shape with the columella in the centre. The space between the columella and the sporangial wall is filled with uni- nuclei, non-motile aplanospore. The spores are liberated by breaking of the sporangial wall they germinate to form new mycelium.

SEXUAL REPRODUCTION

It is isogamous bind gematangial copulation. The sex organs develop when two mating strands + and - comes close to each other. The two gametangia on the opposite strands are formed as protruebalance. The nuclei moves to the tip and separated from the remaining pro-gametangia by a septum. The remaining part forms the suspensor. The wall of the gametangia meets, dissole and the nuclei fuses to form coenozygospore , which develops a thick wall and form a zygospore . On germination it produces a pro-mycelium and a terminal sporangium.

Posted in: Microbiology

Pythium

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Class: Oomycetes

Order: Peronosporales

Family: Pythiaceae

Genus: Pythium

Pythium is a mold of cosmopolitan distribution and consisting of about 45 species which maybe aquatic or terrestrial inhabits. It is facultative parasite on fresh water algae and seedling of many plants like mustard, papaya, tobacco, beans, ginger, etc. it also occurs saprophytic ally in moist soil. Pythium infects the host plant by the wounds. It is also responsible for the “damping- off” disease of seedling. It is also causes “soft rot”,”root rot” etc. it is also involved in decay and decomposition of the plant remains in the soil.

The mycelium of Pythium appears as a white fluffy growth consisting of slender, branched, aseptatic coenocytic hyphae without rhizoids. In the host plant mycelium is both inter and intra cellular without hysteria formation. The cell wall is made up of fungal cellulose and the cytoplasm consists of , many nuclei and other membrane bound organelles like, the mitochondria, ribosome’s, endoplasmic reticulum etc. Reserved food materials are in the form of oil droplets and glycogen.

REPRODUCTION
Reproduction in Pythium is both asexual and sexual.

ASEXUAL REPRODUCTION
It is by the formation of biflagellate zoospore inside zoosporangia both at the tip of the sporangiopore. The sporangium is globule with an epical papilla. Some spices have filamentous or elongated sporangia, which are the same diameter of the hyphae and are they form indistinguishable from hyphae. The sporangiopore maybe simple or in branched. In some spices the sporangia germinates directly into new hyphae and hence they are called cornidium.

SEXUAL REPRODUCTION
It is oogamous and occurs in the formation of terminal oval or spherical oogonium and an elongated antheridium from adjacently on the same mycelium. Fertilization of the female gamete in the oogonium is by the male single functional nucleus in the antheridium which results in the formation of thick walled oospores.

ECONOMIC IMPORTANCE
Pythium dibaryanun causes the “damping-off” tobacco and chilies seedlings.
P. aphanidermatum causes soft rot of apple, papaya and beans.
P.myriotylum causes rhizome rot of ginger.
Pythium is also responsible for decomposition of organic matter in the soil

Posted in: Microbiology

Gracilaria

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Class: Rhodophyceae

Order: Graclariales

Family: Gracilariaceae

Genus: Gracilaria

Gracilaria is common marine red algae found growing attached to the sub-stratum such as rocks by a basal cushion disc, (lithophytes). It has large dichotomously branched thallus also called fronds. It is composed of closely compacted vertical thread like fronds which are which are dark red or pink branches reaching up to 50cm in height.

The matured thallus shows little anatomical difference and T.S of the thallus shows three zones. They are peripheral layer of cell, cortex and medulla. The peripheral layer of cell is small uni or multi nucleated, some of them producing unicellular hairs. Inner to the peripheral layer is the cortex made up of many small cells having ribbon shaped chromatophores. The inner core of the thallus is medulla which contains large iso- diametric cells. The fronds are monosithonous and have a gelatinous envelope on the surface.