Bacteria

  • unicellular Prokaryotes

  • composed of more than 12 separate evolution groups

  • They vary dramatically in how they obtain energy and nutrients, their ecological role and importance to humans

Characteristics

  • DNA is arranged in one circular chromosome

  • No nucleus

  • Plasmid (a small loop of DNA, which does not contain genes for essential cellular functions)

  • Most have a flagella for movement

  • Contains pili which allows the bacteria to attach to other cells or surfaces

  • Some bacteria will have a capsule that provides protection of the cell by reducing water loss, resisting high temperatures and preventing viruses and antibiotics from entering the cell

Shapes of Bacteria

Cocci (singular coccus)

• Spherical

Bacilli (bacillus)

• Rod shaped

3. Spirilla (spirillum)
Spiral

Metabolism

  • Bacteria can be:

  • Autotrophic - they make their own food

  • Heterotrophic - they obtain nutrients from other organic compounds found in living organism or their remains

  • They can either be obligated aerobes (need oxygen) or facultative aerobes (can live with or without oxygen) or obligated anaerobes (can not live with oxygen)

Reproduction: Binary Fission

  • Since they are prokaryotic and lack a nucleus, they reproduce asexually by binary fission.

  • As a cell grows, it makes a copy of its single chromosome. After elongating and separating the two copies, the cell splits into two identical cells. - kinda like mitosis

Reproduction: Conjugationn (transfer chormoseme through tube)

  • In less favourable conditions, DNA can be exchanged instead of reproducing by binary fission.

  • One cell links to another and transfers a copy of some of the chromosome through the tube.

Reproduction: Transformation

  • Bacterial cell picks up loose fragments of DNA, that are released by other cells (usually after cell death).

  • If DNA that is picked up is from another species it is known as horizontal gene transfer.

Endospores

  • When bacteria are in severe conditions that threaten their survival, they can become dormant

  • When they are becoming dormant, they produce endospores which are highly resistance structures that form around the chromosomes when the cell is under stress

  • Living bacterial endospores have been found that are over a thousand years

Benefits of Bacteria

  1. Decomposers - convert atmosphere nitrogen into usable nitrogen for plants

  2. Producers - photosynthetic bacteria are the major producers in aquatic systems

  3. Intestinal bacteria - produce vitamins and has a interdependent relationship with that species, known as mutualism

  4. Food Production - found in cheeses and yogurts

  5. Antibiotics - can be produced naturally by bacterial or synthetically

Negative effects of Bacteria

  • There are thousands of bacteria (pathogens) can cause disease and death in humans and animals; such as typhoid fever, strep throat and tuberculosis

  • Can causes disease in plant and once the plant dies it can remain in the soil for years after the plants have been destroyed

  • Causes food to spoil and go bad

Antibiotic Resistances

  • Occurs when antibiotics are no longer effective in treating bacterial infections as well as they used to be because bacteria change to protect themselves against the antibiotic

  • Each time you take antibiotics, sensitive bacteria are killed. But resistant germs may be left to grow and multiply themselves against the antibiotic

  • Antibiotic resistance is accelerated by the misuse and overuse of antibiotics