Bacteria

Energy & Respiration

How Bacteria Obtain Energy

Some bacteria can make their own food These are called AUTOTROPHS

Some bacteria require that food be made for them These are called HETEROTROPHS

AUTOTROPHS

There are two types of AUTOTROPHS

1. Phototrophic

2. Chemotrophic

Phototrophic Autotrophs

They use the sun’s energy to make their own food (sugar)

Eg’s : Cyanobacteria and photsynthetic Eubacteria

Chemotrophic Autotrophs

They are able to use inorganic molecules (ie: hydrogen sulfides, nitrides, sulphur & iron) as food

They tend to live in harsh environments

Eg: Nitrosomonas uses ammonia as a food source

HETEROTROPHS

There are three types of heterotrophs 1. Phototrophic

2. Chemotrophic

3. Saprotrophic

Phototrophic Heterotrophs

These bacteria are able to use sunlight to produce food molecules but ALSO require organic compounds for nutrition

Very rare

Chemotrophic Heterotrophs

These bacteria take in organic food molecules from their environment to use for energy

Humans are chemotrophic heterotrophs and therefore we often compete with bacteria for the same food source

Eg: Salmonella gets food from raw meat, poultry and eggs. When it grows where food is available it releases poisons which, if the food is not cooked properly, cause food poisoning

Saprotrophic Heterotrophs

These bacteria digest organic matter (food) externally and absorb the resulting nutrients across their cell membranes

Some are involved in recycling matter in ecosystems, these are saprophytic decomposers and are necessary for the functioning of all ecosystems

How bacteria use food energy

There are two processes by which bacteria convert “food” energy into energy that they can use

1. Respiration

2. Fermentation

Respiration

This process requires oxygen to break down food molecules

Therefore it is an AEROBIC process oxygen + sugar carbon dioxide + water 38 ATP produced (ATP = energy molecule)

Fermentation

This process does NOT require oxygen to break down food molecules to produce energy

Therefore this is an ANAEROBIC process 2 ATP produced

Classification based on respiration

There are three classifications of bacteria based on their mode of respiration 1. Obligate aerobes 2. Obligate anaerobes 3. Facultative anaerobes

Obligate Aerobes

These bacteria carry out aerobic respiration

They MUST live in oxygen rich environments to survive

Obligate Anaerobes

These bacteria carry out fermentation to produce energy from food

They must live in environments where there is NO oxygen

If oxygen is present they will die

Facultative Anaerobes

These bacteria usually carry out aerobic respiration

If deprived of oxygen they can switch to anaerobic fermentation for a short time

Summary-Complete the tablesEnergy Source

Autotrophs Heterotrophs

Phototrophic

Chemotrophic

Saprotrophic

Respiration

Aerobes Anaerobes

Obligate

Falcultative