These organisms are most primitive. There are the first inhabitants of the earth, and they still continue to flourish. Bacteria are the sole members of this kingdom. They occur almost everywhere. Hundereds of bacteria are present in a handful soil. They were live in extreme habitats such as hot springs, deep oceans, deserts and snow where very few other life forms can survive.
Characters of Kingdom Monera
- They are unicellular, colonial or filamentous, prokaryotic organisms without nuclear membrane, nucleolus, chromatin and histone proteins.
- Nucleoid or incipient nucleus is composed of naked DNA, RNA and non – histone proteins. DNA is circular and double stranded.
- Cell wall is made up of peptidoglycan (Amino acids + Sugar) except in Archaebacteria and Mycoplasma.
- Membrane bound cell organelles are absent.
- Ribosomes are 70S type.
- Some of the bacteria are autotrophic but vast majority are heterotrophic.
- Respiratory enzymes present associated with plasma membrane.
- Reproduction is asexual type.
- Bacteria show both autotrophic and heterotrophic nutrition. Autotrophic nutrition involves synthesis of organic material from inorganic substances with the help of light energy (photosynthetic autotrophic) or chemical energy (chemosynthetic autotrophic). Majority of them show heterotrophic nutrition which involves the obtaining of readymade organic nutrients from outside sources. It is of three types — saprotrophic, parasitic and symbiotic.
On the basis of their shape, bacteria are grouped under four categories:
- The Sperical Coccus (pl.: Cocci)
- The rod – shaped Bacillus (pl.: Bacilli)
- The comma – shaped Vibrium (pl.: Vibrio), and
- The spiral Spirillum (pl.: Spirilla)