Lecture 9

Question 1

Why are some bacteria non-culturable (for known species)?

Answer 1

1. cells may have entered a non-culturab mle state (VBNC) or
2. cultivation techniques are known but were not used

Question 2

Why are some bacteria non-culturable? (for uncharacterized bacteria)

Answer 2

1. the cells may be i aVBNC state
2. They would grow but correct cultivation techniques were not used
3. We are currently not able to culture them (we may or may not ever be able to grow them)

Question 3

What are some factors of species that have never been cultured?

Answer 3

• May require complex growth factors
• May require complex host factors
• symbionts, pathogens, and sepcies involved in other intimate metabolic associations
• may only grow with other species within complex consortia
• may be very slow growing
• may not attain high cell densities
• may not form colonies
• etc.

Question 4

What is the VBNC state?

Answer 4

viable but not culturable

- possibly dormant state

Question 5

What are some best known VBNC examples?

Answer 5

• Salmonella entertidis, Vibrio cholerae

Can enter VBNC state when exposed to certain conditions: - Salt water (osmotic shock)

• Fresh water (osmotic shock)
• Low temperature (cold shock)

Difficult/impossible to revive aftersuch shocks

Question 6

how do we know salmonella entertidis and vibrio cholerae are not dead when in dormant state?

Answer 6

• Retain ability to infect and induce disease in HOST even though they fail to grow in culture under standard conditions
• possibly dfficult for cells to survive the oxidative burst that may occur when placed in nutrient-rich culture media for revival after having been in a dormant state

Question 7

Do we know anything about non-culturable species?

Answer 7

• Yes, but only of a very few, if they can be identified under a microscope on the basis of unique features and lately via techniques such as FISH
• A certain amount about their physiology can be hypothesized from appearance and ecological context
• phylogenetic information may allow some things to be guessed regarding physiology, etc, but cells need to be cultured for in-depth physiological characterization
• I is now possible, in some cases, to obtain genome sequence information from cells without culturing them

Question 8

What is the name of the bacteria that is an obligate symbiont in gut of tropical surgeon fish?

Answer 8

Epulopiscium fishelsoni

Question 9

What is the name of the giant sulfur bacterium “sulfur pearl of namibia”?

Answer 9

Thiomargarita Namibiensis