Monera is kingdom of prokaryotes. Therefore, it is also known as prokaryota. Members of Monera are adapted to all types of habitats, because it includes the most primitive and earliest forms of life. Bacteria are the simplest life forms on earth. They exist everywhere on the planet. Bacteria live in environments no other living thing can tolerate, such as thermal hot springs and supersaturated saline environments. They can live within other living organisms. Bacteria can live at the bottom of the ocean, near deep sea vents, where the water temperature is close to 400oC. Bacteria were probably the earliest life forms on earth.
Characteristics Of Monera
- Monerans are basically unicellular prokaryotes and contain the most primitive form of life.
- On the basis of nutrition they are saprotrophic, parasitic, chemoautotrophic, photoautotrophic and symbiotic.
- On the basis of respiration they may be aerobic or anaerobic.
- Cell wall is generally present. It contains peptidoglycan and polysaccharides (other than cellulose). Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane.
- Cell membrane is present and made of lipoprotein.
- Cytoplasm of bacteria or monera lacks membrane bound cell organelles liek mitochondria, lysosome, golgibody, plastids etc.
- Genetic material is not organised into a nucleus. Instead of nucleus, they have nucleiod. Nucleiod doesn't has nuclear membrane and nucleolus.
- DNA is naked, i.e. it is not associated with histone proteins. DNA is circular. DNA combined with non histone protein is known as nucleiod. It is equivalent to one chromosome.
- Besides nuclear DNA, in some bacteria extra-chromosomal DNA are present which is knwon as plasmid.
- In prokaryotes ribosomes are of 70s type.
- Reproduction is done by asexual reproduction but in some case gene recombination also take place.
Shape Of Bacteria
Bacteria have variations in their shape. On the basis of their shape bacteria are of following types:
- Coccus/Cocci :They are spherical shaped.
- Bacillus/Bacilli : They are rod shaped.
- Spirillum/Spirilla :These are spiral shaped bacteria.
- Comma/Vibrio :These are comma shaped bacteria.
- Bacili are most abudant bacteria.
- Coccus are smallest and maximum resistant bacteria.
Note: There are some prefixes also used to show how bacteria group themeselves together. They self-organize into long chains, grape-like clusters, or paris. For pair arrangement we use "diplo-" prefix. For chain arrangement we use "strepto-" prefix. For clusters arrangement we use "staphylo-" prefix. Example: The bacteria that cause the disease strep throat are called Streptococcus. The prefix "strepto-" means chain, and the "coccus" means sphere". It means these bacteria are spherical in shape and grouped in chain like structure.
Some Important Point
- Anton von leeuwenhoek first saw bacteria.
- Louis pasteur gave germ theory of diseases.
- Robert Koch first of call cultured bacteria.
- The branch biology which deals with study of bacteria is known as bacteriology.
There are three types of plasmid:
- F-factor or fertility factor: It is responsible for transfer of genetic material.
- R-factor or resistance factor: It provides resistance against drugs.
- Colicinogenic factor: It produces colicines which kill other bacteria.
Classification Of Bacteria
There are two major groups of bacteria: