Bacterial Nutrition and Growth

Question 1

Why do we care about bacterial nutrition?

Answer 1

• affects how we grow bacteria in lab
• affects how we differentiate types of bacteria
• is the underlying fundamental reason for bacterial infection

Question 2

What do all cells require to grow?

Answer 2

Source of carbon and energy

- nitrogen, phosphorus, sulfur, sodium, potassium, iron, magnesium, manganese, and other minerals

Question 3

Photosynthetic

Answer 3

Use light as the sole source of energy for growth and carbon fixation form carbon dioxide
- no pathogens

Question 4

Autotrophic

Answer 4

Use inorganic molecules as the sole energy source and may use carbon dioxide or other organic molecules as a carbon source

• chemolithotrophic
• no pathogens

Question 5

Heterotrophic

Answer 5

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

Question 6

Nutrient requirements of heterotrophic bacteria

Answer 6

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

Question 7

Glucose

Answer 7

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

Question 8

Fastidious microorganisms

Answer 8

Are missing enzymes in one or more biosynthetic pathways and therefore require other nutrients besides glucose
- require preformed nutrients in the growth medium

Question 9

Some bacteria can utilize other biomolecules (ex: lactose) as energy/carbon sources by converting them into ____

Answer 9

Glucose

• glucose is basic building block for biosynthesis
• glucose is always preferred energy/carbon source
• alternative energy sources are conserved within species

Question 10

Essential nutrients

Answer 10

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

Question 11

Nonessential nutrients

Answer 11

Includes any molecules that a bacteria is capable of synthesizing, but will salvage if available

Question 12

Energy cost for obtaining nutrients

Answer 12

1st: salvaged preformed nutrients cost the least energy
2nd: glucose
3rd: other carbon sources that can be converted to glucose cost the most

Question 13

Types of heterotrophic bacteria

Answer 13

• 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)

Question 14

Facultative parasites

Answer 14

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

Question 15

Obligate parasites

Answer 15

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

Question 16

Parasitic bacteria can be either ____ or ______

Answer 16

Commensal or pathogenic

• commensal cause no harm or benefit to the host
• pathogenic cause some harm to host

Question 17

Opportunistic pathogens

Answer 17

Can be commensal or pathogenic depending on the circumstance

Question 18

Why do some heterotrophic bacteria invest so much energy into adapting pathogenic mechanisms to allow them to survive in the hostile host environment?

Answer 18

Eukaryotic tissues are an extremely nutrient rich growth medium

Question 19

Bacterial media

Answer 19

Bacteria can be cultured in either broth medium or on agar plates (same media can be used for both)

Question 20

Agar plates

Answer 20

Allow the isolation of colonies that are derived from a single bacterium

Question 21

Broth cultures

Answer 21

Allow growth of large batches of bacteria

- shaking is required to oxygenate a broth culture

Question 22

Complex media

Answer 22

Not chemically defined, usually contain a biological fluid or component such as blood, serum, or enzymatic digests of protein
- ex: yeast extract or brain heart infusion

Question 23

Chemically defined media

Answer 23

Every component is known and is present at a defined concentration

Question 24

Differential media

Answer 24

Some type of indicator system is added to the media

- ex: blood for detection of hemolysis, or specific carbs and a pH indicating dye to detect fermentation

Question 25

Selective media

Answer 25

Some type of indicator is added to prevent growth of certain bacteria - selects for growth of desired bacterial species - ex: antibiotics, high salt concentration, bile salts, growth inhibiting dyes

Question 26

Enrichment media

Answer 26

A liquid cultural medium that permits preferential emergence of certain bacteria that initially may have made up a relatively minute proportion of a mixed population

Question 27

Transport media

Answer 27

Used for the temporary storage of specimens being transported to the lab for cultivation - ideally maintains the viability of all organisms in the specimen without altering their concentration - typically contain only buffers and salt

Question 28

Blood agar

Answer 28

Complex differential medium | - detects hemolysis

Question 29

MacConkey agar

Answer 29

Selective differential medium - bile salts and crystal violet inhibit gram-positive and many gram-negative species - lactose and neutral red cause lactose fermenting colonies to turn pink