Bacterial Nutrition and Growth Flashcards
Why do we care about bacterial nutrition?
- affects how we grow bacteria in lab
- affects how we differentiate types of bacteria
- is the underlying fundamental reason for bacterial infection
What do all cells require to grow?
Source of carbon and energy
- nitrogen, phosphorus, sulfur, sodium, potassium, iron, magnesium, manganese, and other minerals
Photosynthetic
Use light as the sole source of energy for growth and carbon fixation form carbon dioxide
- no pathogens
Autotrophic
Use inorganic molecules as the sole energy source and may use carbon dioxide or other organic molecules as a carbon source
- chemolithotrophic
- no pathogens
Heterotrophic
Cannot use inorganic molecules as the sole source of energy and cannot use carbon dioxide as the sole source of carbon
- use organic molecules as source of energy and carbon
Nutrient requirements of heterotrophic bacteria
All complex molecules required for life (carbs, fats, nucleic acids, and proteins) must be obtained by either synthesis from simpler molecules or salvaged from the environment
- requires less energy to salvage nutrients than to synthesize them
- glucose is basic carbon source used to synthesize biomolecules
Glucose
Serves as the energy source and carbon source for synthesis of nucleic acids, proteins, lipids, and carbs
- some heterotrophs have all the biosynthetic pathways required to make what they need from glucose
- ex: E. coli
Fastidious microorganisms
Are missing enzymes in one or more biosynthetic pathways and therefore require other nutrients besides glucose
- require preformed nutrients in the growth medium
Some bacteria can utilize other biomolecules (ex: lactose) as energy/carbon sources by converting them into ____
Glucose
- glucose is basic building block for biosynthesis
- glucose is always preferred energy/carbon source
- alternative energy sources are conserved within species
Essential nutrients
Required for cell growth
- nutrients required by all heterotrophic bacteria: carbon source, nitrogen source, and other minerals
- nutrient requirements specific for each species based on what they are not capable of synthesizing
Nonessential nutrients
Includes any molecules that a bacteria is capable of synthesizing, but will salvage if available
Energy cost for obtaining nutrients
1st: salvaged preformed nutrients cost the least energy
2nd: glucose
3rd: other carbon sources that can be converted to glucose cost the most
Types of heterotrophic bacteria
- some are saprophytic, utilizing dead or decaying organic material
- some are parasitic, obtaining nutrients from other organisms (obligate parasites)
- some are capable of both saprophytic and parasitic lifestyles (facultative parasites)
Facultative parasites
Can grow on dead/decaying material as well as reproduce in the host and cause disease
- the more fastidious (require complex media) a bacterial species is, the more adapted it is to the parasitic lifestyle = it has become more dependent on host to provide complex nutrients
Obligate parasites
Can only grow in or on a host and cannot grow on artificial media
- cannot synthesize the nutrients they need to reproduce outside the host
- host or cell specificity of a pathogen may be due to nutrients they require only being available in a specific host environment
