What is the definition bacteria?

Answer 1

The name bacteria is from the Greek bacterion ("little stick", i.e. the rod forms).

Bacteria are unicellular prokaryotic microorganisms. Bacteria are the smallest in size and largest in number among living organisms. Bacteria were first discovered by Dutch scientist Anton van Leeuwenhoek in 1675 in rain water, then in pond water and in scrapings from his teeth. He considered them animalcules.

They show some plant-like characteristics such as the presence of rigid cell walls and reproduction by spores. The average size varies in micrometers as the smallest one is cocci i.e. from 0.5-3.5 microns and largest is spirillum 15-22 microns.

They can be rod-like ( E.col, Rhizobium), or spherical, monococcus, dicoccus, streptococcus (in chain), staphylococcus( in an irregular bunch), helical, vibrio, spiral, or filamentus. Sometimes they are pleomorphic e.g. Acetobacter.

They may be chemolithotrophs or chemoautotrophs, or heterotrophs.

Reproduction is either vegetative or asexual ( by conidia, or endospores). True sexual reproduction and alteration of generation are absent in bacteria, and can be done by conjugation, transformation and transduction.

According to six-kingdom classification the bacteria comes under Monera i.e. of prokaryotes. According to the Cavalier-Smith two EMPIRE and eight KINGDOM classification the bacterial Empire contains two kingdoms the Eubacteria and the archaeobacteria.
(Biol.) A microscopic single-celled organism having no distinguishable nucleus, belonging to the kingdom Monera. Bacteria have varying shapes, usually taking the form of a jointed rodlike filament, or a small sphere, but also in certain cases having a branched form. Bacteria are destitute of chlorophyll, but in those members of the phylum Cyanophyta (the blue-green algae) other light-absorbing pigments are present. They are the smallest of microscopic organisms which have their own metabolic processes carried on within cell membranes, viruses being smaller but not capable of living freely. The bacteria are very widely diffused in nature, and multiply with marvelous rapidity, both by fission and by spores. Bacteria may require oxygen for their energy-producing metabolism, and these are calledaerobes; or may multiply in the absence of oxygen, these forms being anaerobes. Certain species are active agents in fermentation, while others appear to be the cause of certain Infectious Diseases. The branch of science with studies bacteria is bacteriology, being a division of microbiology. See Bacillus. [1913 Webster +PJC]

Answer 2

Bacteria-

ubiquitous one-celled organisms, spherical, spiral, or rod-shaped and appearing singly or in chains, comprising the Schizomycota, a phylum of the kingdom Monera (in some classification systems the plant class Schizomycetes), various species of which are involved in fermentation, putrefaction, infectious diseases, or nitrogen fixation.

Answer 3

Bacteria (one of them is a bacterium) are very small organisms. Exactly all bacteria are so tiny they can only be seen from first to last a microscope. It is correct to say the soil sample contains millions of bacteria. Bacteria are microscopic living organisms, usually one-celled, that can be found everywhere.

Answer 4

Bacteria are single-celled microorganisms that exist in various environments. They are often categorized as prokaryotic organisms due to their lack of a nucleus and other membrane-bound organelles. Some bacteria are beneficial and play important roles in processes like digestion, while others can cause infections and diseases.

Answer 5

Single celled microorganisms that can reproduce very rapidly. Many bacteria are useful, e.g gut bacteria and decomposing bacteria, but some cause disease.

Answer 6

kingdom- animalia

Answer 7

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