Bacteria

Bacteria

• Bacteria are the smallest "living" organisms
• Are prokaryotic cells
• Lack Nucleus
• DNA is naked. - a single loop - not bound into a chromosome.
• May contain plasmids (small circular fragments of DNA)
• Lack membrane-bound organelles
• Usually have an outer Cell Wall.
• Sometimes have an Outer Capsule - These stain red in a Gram Stain test and are called Gram Negative bacteria.
• Those without an outer capsule stain blue in the gram stain test and are called Gram Positive Bacteria

• There are 4 Phyla of bacteria

1. Eubacteria ("True" bacteria)
2. Cyanobacteria - aka. Blue-green bacteria - contain chlorophyll a, & phycocyanin (bluish pigment) - These are photosynthetic bacteria.
3. Archaebacteria - primitive bacteria, frequently found in harsh environments (eg. Hot springs, animal gut, thick mud, high salt concentrations)
4. Prochlorobacteria - contain both chlorophyll a & b. Similar to chloroplasts found in eukaryotic cells.

• Bacteria have 3 basic shapes:

1. Spherical - cocci
2. Rod-shaped - bacilli
3. Spiral - spirilli

How Bacteria obtain energy:

• Two major categories:

1. Autotrophs - Make their own energy - 2 types

• Phototrophic autotrophs - Get energy from sunlight
• Chemotrophic autotrophs - Get energy from inorganic molecules (eg. Sulfides)

1. Heterotrophs - Energy obtained from other organisms

• Chemotrophic heterotrophs - obtain energy by dissolving/absorbing organic material
• Phototrophic heterotrophs - meet some energy needs from photosynthesis, but must absorb organic compounds.

Bacterial Respiration:

• 3 major categories

1. Obligate aerobes. - Must have O₂ in order to live
2. Obligate anaerobes - Must live in an O₂ free environment
3. Facultative anaerobes - Can live with or without O₂.

Bacterial Reproduction:

• Bacteria reproduce through binary fission.
• Can engage in primitive sexual reproduction called conjugation.
• A bridge is formed between 2 bacteria
• Plasmids are shared across bridge, thus exchanging genetic information.
• In times of harsh conditions, bacteria can form endospores, to encapsulate themselves in a dormant state, until conditions improve.

Motility
Some bacteria are motile - can move by either thrashing, secreting lubricating secretions or through use of a flagellum.

Flagellated bacteria

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