Nitrogen Fixations

• Process by which nitrogen in the atmosphere is converted into a form that can be used by living things

All bacteria are ProkaryotesGeneral Characteristics of Bacteria

• All are single-cell organisms, rarely cluster as multicellular in cyanobacteria

• No nucleus or other membrane-bound organelles (mitochondria, chloroplasts)

• Metabolic reactions occur in folds of plasma membrane

• Cell wall (Functions as a protective barrier) is composed of peptidoglycan found in most cells

• External layers may be present as capsule or slime layer

• Genome is DNA (single, circular chromosome without histones) in “nucleoid” 2

• Flagella (whip-like structures) when present consist of fibris of flagellin

• Pili (Short, hair-like, thin appendages) when present as attachment or conjugation pili

• Cell division by binary fission (DNA molecule is replicated, separated and attached to the cell membrane; then the cell splits into two identical cells, each containing an exact copy of the original cell's DNA)

•Bacteria can perform both anaerobic and aerobic respiration

• Many aquatic bacteria have gas vacuole (filled with gas) enable the bacteria to float

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1) Some make antibiotics (Streptomyacin)

2) Provide enzymes for biological washing powders

3) Used as microbial insecticides

4) Used to make biodegradable plastics & leach out metals

5) Decomposers – Analysis of dead bodies and substances in soil, inside animals Enterobacteria – live inside us, break down waste, make vitamins

6) Process foods – cheese, yogurt (convert lactose to lactic acid), produce characteristic flavour

Biological Importance of Bacteria

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7) Xanthan gum formed by certain bacteria is used as gelling agent in many industries

8) Bacteria are used in molecular research, genetic engineering, and medical research

9) Some bacteria ferment sugars & organic acids and produce ethanol, methanol, acetone, lactic acid & acetic acid

10) Bacillus thuringiensis (BT) used as biological control of pests. BT reproduce only in intestinal tract of caterpillars which are killed by toxin from the bacterium

11) Lactobacillus used in the dairy, beverage and baking industries. Used in production of wine, beer and other commercial products

12) Actinomycetes (nonphotosynthetic bacteria with branched filaments) were original source of antibiotics as tetracycline, neomycine, erthromycin & streptomycin

Streptomycin is produced by Streptomycetes

13) The cyanobacterium Spirulina has a dry weight protein content of about 70 %.

So it is used as a nutritional food supplement