Bacteria Reproduction and Metabolism

Bacteria Take Over!Under ideal stable conditions, bacteria can multiply

at alarming rates…

Bacteria can grow and divide every 20-30 min.

Within 15 hours, a single cell could have multiplied into 1,000,000,000 cells

In 24 hrs. the mass of cells would weigh over 2000 tons

Within a week, the bacteria would weigh More than the earth…

So… Why don’t bacteria take over the earth?

Conditions for Growth

• Several environmental factors must be within a bacterium’s optimal range for it to grow and divideo Moistureo Temperatureo pHo Nutrition

• Different species have specific requirements in order to grow and reproduce

Endospores• When some bacillus bacteria and other types

are exposed to extended periods of unfavorable conditions, they are capable of forming endospores• Endospores have several layers of hard materials protecting the bacteria’s DNA• This allows them to withstand:• 20 hours of boiling• Freezing• Extreme dryness• Extreme pressure• Poison gas and harsh chemicals

Endospores• Examples:• Bacillus anthracis (anthrax) • Clostridium tetani (tetanus or lockjaw)

• Bacteria that form endospores are of particular interest because they can survive thousands of years and become resistant to antibiotics

Nutrition

• Bacteria are classified into 2 main groups based on how/where they obtain their food:

1. Autotrophs – Are able to make their own food using sunlight or chemicals

• Photosynthetic• Chemosynthetic

Nutrition

2. Heterotrophs – must obtain their food from other sources than themselves• Parasitic – feeding on a living host

for nutrients• Obligate parasites go a step further

and require living tissue in order to grow

• Saprophytic – feeding on dead organic matter for nutrients

Bacteria and Oxygen

• Louis Pasteur demonstrated that some bacteria can grow without (and are actually inhibited or destroyed by) free oxygen•Obligate anaerobes – organisms that grow only in the absence of free oxygen•Obligate aerobes – organisms that grow only in the presence of free oxygen•Facultative anaerobes – organisms that can grow with or without oxygen

Reproduction

• Binary Fission•Asexual•Time Frame:• From once/20

minutes to 2-3 days

Reproduction• Conjugation – a process in which bacteria

exchange or transfer genetic information• Since there is no meiosis involved and not all genes are transferred it is not considered true sexual reproduction

• Bacteria exchange DNA through the pili structures