Question

Diagram and describe the following prokaryotic structures: cell wall, flagella, fimbriae, inclusions, nucleoid (chromosome and plasmids), and pili.

Describe examples of how prokaryotes can benefit as well as harm humans.

Distinguish among the following groups of bacteria: cyanobacteria, mycoplasmas, phytoplasmas, prochlorophytes, purple bacteria, and green bacteria.

Answer 1

A unicellular organism, which lack the internal membrane bound structures or the organelles commonly termed as prokaryotes. These organisms do not contain the nucleus but having the single chromosome. The given prokaryotic structures can be described as follows.

Cell wall: lipopolysaccharides, proteins, and phospholipids are the main components of the cell wall of gram negative bacteria. Peptidoglycan is the main component of the cell wall of gram positive bacteria. The cell-wall helps in maintaining the structural integrity of the cell.

Flagella: a whip-like structure come out from the cell-wall of the bacteria is termed as flagella. This structure help in the movement of the bacteria. There are three basic components of the flagella. A motor complex, a whip-like filament, and the hook that connect them are three basic components.

Fimbriae: the protein tubes that are the extended forms of the outer membrane are called as fimbriae.This structure usually found in the membranes of proteobacteria. Fimbriae help in the attachment and present in the large number.

Inclusion: the nonliving components of the cell are called as inclusions. The inclusions do not contain the metabolic activity. these are not membrane bound as well. Lipid, glycogen, crystals, droplets, and pigments are the inclusions.

Nucleoids

Chromosome: the bacerial chromosome is usually present in the circular form. There are no any free ends present in the circular DNA of the prokaryotes.

Plasmid: plasmids are the independent small pieces of the DNA. Plasmid is also called as extra chromosomal DNA. Most of the bacteria also contain plasmid along with the circular DNA. The plasmids can be transferred easily between the bacteria during the horizontal gene transfer.

The prokaryotes can be the both, friends or foes of the human being.

Helpful bacteria: Streptomyces help in making the antibiotics. Rhizobium is a bacteria that help in the nitrogen fixation. This bacteria found in the soil.

Harmful bacteria: Salmonella is the bacteria that can cause diarrhea. This bacterium is usually fund in the food products. Listeriosis is another harmful bacteria that can cause illness in the human being.

The differences among the given bacteria are described in the given table:

Cyanobacteria	Mycoplasmas	Phytoplasmas	Prochlorophytes	Purple bacteria	Green bacteria
Cyanobacteria belongs to the phylum called as Cynophyta. this bacteria have cell-wall that contain peptidoglycan.	Mycoplasma lack the cell-wall.	Phytoplasmas also lack the cell-wall.	Prochlorophytes belongs to the algal sub-class known as prochlorophyta.	Purple bacteria are the pigmented bacteria. they contain cell membrane and bacteriochlorophyll pigments.	These bactria belongs to the phylum Chloobi. these bacteria contain diversity in their cell-wall.
This bacteria is able to produce oxygen as it gain its energy through the photosynthesis.	Mycoplasmas are the fucultative anaerobes.	These are the obligate parasites of the phloem of plant.	Prochlorophyta is a group of bacteria that are photosynthetic in nature. They contain blue phycobilin pigments.	These are also the photosynthetic bacteria that produce their own food.	These are anoxygenic phototrophic bacteria.