Explain the characteristics of bacteria.

1. Cell wall structure
Bacteria are classified by their different cell wall structures – Gram stain
- The cell walls are defined by a series of reagents of stains Gram negative bacteria have a thin wall layer and an outer membrane that stains red
- Gram positive bacteria have a thick wall layer, stains violet and no outer membrane

2. Gaseous oxygen requirement
Bacteria react to gaseous oxygen in one of the three ways (a) Anaerobic bacteria die when exposed to oxygen (they obtain energy from other compounds). Facultative anaerobes- can survive with or without oxygen, but prefer to be in oxygen environments. Obligate aerobes- require oxygen

3. Energy sources
Bacteria obtain energy from a variety of sources.
Heterotrophs- obtain energy by consuming and breaking down complex organic compounds. Autotrophs - create energy through photosynthesis or chemosynthesis.

4. Temperature requirements
Most bacteria thrive at temperatures at or around that of human body 370C (some are normal flora of human intestines e.g E.coli).
Mesophiles (moderate temperature loving) – 25-400c.
Psychrophiles – prefer cold temperatures some 00c – 150c – live in artic regions temperatures
Physchrotrophs - 20-300c – often associated with food spoilage.
Thermophiles – Thrive in very hot environments (500C - 600C) in hot springs. Extreme thermophiles (910c) others hydrothermal vent on ocean bottom (3500c).
5. PH requirement
- Most grow optimally within a narrow range of PH-between 6.7 and 7.5.
- Acidophiles – can survive at PH 1 (Thiobacillus Ferroxidans)
- Alkalophiles – thrive at PH 9.0 (vibro cholerae)

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Kavungya answered the question on March 12, 2019 at 13:20