lysogenic bacterium

bacterium /bac·te·ri·um/ (bak-tēr´e-um) pl. bacte´ria   [L.] in general, any of the unicellular prokaryotic microorganisms that commonly multiply by cell division, lack a nucleus or membrane-bound organelles, and possess a cell wall; they may be aerobic or anaerobic, motile or nonmotile, free-living, saprophytic, parasitic, or pathogenic.bacter´ial

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acid-fast bacterium  one not readily decolorized by acids after staining.

coliform bacterium  one of the facultative, gram-negative, rod-shaped bacteria that are normal inhabitants of the intestinal tract; see Escherichia, Klebsiella, and Serratia.

coryneform bacteria  a group of bacteria that are morphologically similiar to organisms of the genus Corynebacterium.

gram-negative bacterium  see gram-negative, under G.

gram-positive bacterium  see gram-positive, under G.

hemophilic bacterium  one that has a nutritional affinity for constituents of fresh blood or whose growth is stimulated by blood-enriched media.

lysogenic bacterium  a bacterial cell that harbors in its genome the genetic material (prophage) of a temperate bacteriophage and thus reproduces the bacteriophage in cell division; occasionally the prophage develops into the mature form, replicates, lyses the bacterial cell, and is free to infect other cells.

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lysogenic bacterium

n.

A bacterium whose genome includes the genome of a temperate bacteriophage.

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bacterium

pl. bacteria [L.] any prokaryotic microorganism. Bacteria are single-celled microorganisms that differ from all other organisms (the eukaryotes) in lacking a true nucleus and organelles such as mitochondria, chloroplasts and lysosomes. Their genetic material consists of a single double-stranded DNA molecule, whereas the genetic material of eukaryotes consists of multiple chromosomes, which are complex structures of DNA and protein.

Bacteria reproduce by binary fission and generally have a very high rate of population growth and mutation. Genetic material can be transferred between bacteria by three processes: transformation (absorption of naked DNA), transduction (transfer by a temperate bacteriophage), and conjugation (transfer by independently replicating DNA molecules, called plasmids). Some bacteria can also form spores, dehydrated forms that are relatively resistant to heat, cold, lack of water, toxic chemicals and radiation.

Most bacteria have a rigid cell wall outside of the cell membrane primarily composed of a dense layer of peptidoglycan, a network of polysaccharide chains with polypeptide cross-links. Some antimicrobial agents, the penicillins and cephalosporins, act by interfering with peptidoglycan synthesis.

Bacteria can have any of three types of external structures: flagella, which are rotating locomotor organelles; pili or fimbriae, which are minute filamentous appendages; and a capsule, which is a layer of gelatinous material around the cell. Large pili called sex pili are involved in conjugation while other pili are involved in adherence of bacteria to mucosal surfaces. The capsule is associated with virulent strains of bacteria and protects the bacterium from phagocytosis. See also bacteria.

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acid-fast bacterium

one that, because of wax-like composition of the cell wall, is not readily decolorized by acids after staining, especially Mycobacterium spp.

coliform bacterium

particularly found in the gut (colon) of animals. See aerobacter aerogenes, escherichia and paracolobactrum.

hemophilic bacterium

microorganisms of the genera Haemophilus and Bordetella, which have a nutritional requirement for fresh blood or whose growth is significantly stimulated on blood-containing media.

lactic acid bacterium

bacteria that, in suitable media, ferment carbohydrates to form lactic acid.

lysogenic bacterium

any bacterial cell harboring in its genome the genetic material (prophage) of a temperate bacteriophage and thus reproducing the bacteriophage DNA in each cell division; occasionally the prophage becomes nonintegrated (induced), replicates, lyses the bacterial cell, and is free to infect other cells.