Protozoa

Most of the protozoa are unicellular, aerobic, and chemoheterotrophic in nature. Reproduction is through sexual as well as asexually. They also require high moisture for their growth as algae. They have specialized structures to take food. Protozoa usually covered with pellicle. Digestion occurs in vacuoles. Their life cycle switch between two forms; one is trophozoite (vegetative and growing stage), and another one is cyst stage. This is the survival stage for protozoa where they will move from one host to another, resisting to the different environmental conditions. Cyst will turn back to their vegetative stage when it finds favorable conditions.

Based on gene sequencing and motility it has been grouped into five major phyla

1. Archaeoa

Archaeoa are spindle shaped, lack mitochondria. They are having flagella at the front end and common symbionts in animal. Example- Giardia

2. Apicomplexa

Organisms present in this groups are obligate intracellular parasites, and non motile in mature form. Usually transmitted by insects, and having complex life cycle with different stages in different hosts. Example- Plasmodioum (malaria)

3. Amoebozoa

This group contains causative agent of dysentery, and they move with the help of pseudopods. Example- Entamoeba

4. Ciliophora

Only one pathogen in group called Balantium coli, which is also a causative agent of dysentery. They move with the help of cilia present on the surface of cell. Example- Paramacium.

5. Euglenozoa

Asexual mode of reproduction and movement with the help of flagella called zooflagellates. It contains two groups; a) Euglenoids: they are photoautotroph as well as chemoautotrophs, has chlorophyll a, movement via flagella, b) Hemoflagellates: they are long slender cells with undulating membrane and flagellum. Transmitted through insects and live in host blood as the name implies. Example- Trypansoma

Slime Molds

They are having both the properties of fungi and amoeba, and mostly related to amoebazoa. They are the parasites of bacteria and fungi and produce spores in unfavorable conditions. It has been divided into two phyla; cellular slime molds and plasmodial slime molds.

1. Cellular slime molds

In favorable conditions, they exist as unicellular amoeba and in unfavorable conditions; they form as aggregate of multicellular mushroom like structure to generate spores. When return to favorable conditions, spores germinate into unicellular amoeba.

2. Plasmodial slime molds

In favorable conditions, they exist as plasmodium containing multinucleated mass of protoplasm. They used to adapt amoeba like movement. In unfavorable conditions, they form into mycelium, which in turn produces spores on aerial hyphae. When it returns to the favorable conditions, spores germinate and undergo rapid cell division to form new plasmodium.

 

REFERENCES:

Text Books:

1. Jeffery C. Pommerville. Alcamo's Fundamentals of Microbiology (Tenth Edition). Jones and Bartlett Student edition.

2. Gerard J. Tortora, Berdell R. Funke, Christine L. Case. Pearson - Microbiology: An Introduction. Benjamin Cummings.

Reference Books:

1. Lansing M. Prescott, John P. Harley and Donald A. Klein. Microbiology. Mc Graw Hill companies.

2. Biology, Raven and Jhonson, 6 th edition (2001)

3. Microbiology, Pelczar. M.J , Chan E.C.S, Kreig N.R, 5th edition (2007)