VBNC Flashcards
VBNC
Viable but nonculturable state
-Bacterial cells maintain viability and metabolic activity but cells do not grow and do not multiply on/in routine (medium that B usually grow on) bacteriological culture media
VBNC prupose
Cells enter in response to environmental stresses, thus making for long term survival in environment
-It is a state where they are nonculturable until they exit the state
VBNC genera
16 genera
include:
-Enterobacteriaceae
-Vibrionaceae
Problem with estuarine bacterium
Includes Vibrio vulnificus
-USA: 52,000 illnesses and 100 deaths
-seafoods and tatoos (after you get into water body)
-Wound infections lead to 25-50% mortality rate
VBNC triggers
Environmental stresses such as:
-Temp, salt conc, oxygen conc, level of light, selective media, growth limitng factors
Graph of VBNC
Resuscitation from VBNC
-several structura; changes
-Changes in synthesis, respiration state and nutrient transport
Vibrio vulificus resuscitation
within 8 hours from stress there will be some culturable cells
within 12-24hr: same amount of cells will be found as before stress
Legionella pneumophila VBNC
Entry = nutrient deprivation
Growth curve for batch culture
Lag
exponential
stationary
death
Exponential growth
B divide at constant intervals with max growth rate
Arithmetic scale is constantly increasing slope
log scale is straight line
generation time/ doubling time
Pop will double in number specific length of time
Future pop size formula
n formula
Growth rate constant formula
Generation time formula
Detection and enumeration of VBNC
- Acridine orange direct counting
- Fluorescent Ab (or DNA probes)
- Direct viable count
Acridine orange DC
Treat cells with acridine orange:
DNA will show up as green and RNA as orange
RNA indicates cell is metabolically activey
Acridine weakness
CAnt differentiate between low and no RNA
Fluorescent Ab
Use fluorescent antibodies or DNA probes
-Cannot differentiate between dead and viable cells
DVC
Direct cell counts
-can be combined with fluorescent ab
-Nalidixic acid inhibits DNA synthesis (but allows cells to elongate without dividing which enables the determination of viability)
-Yeast extract is added
-Morphology is NB as viable will be rod-shaped
AS yet uncultivated
Media and culture conditions not adequate or unsuitable
-often for B that have never been cultivated
Test food and water
Food:
homogenise food
-dilution series
-do streak plates
-determine CFU/g
water:
-Filter water and then overlay filter over agar to determine CFU/ml
Why growth only occurs after 7hr
B are used to very little nutrients and so pumps in too much after exposure
-Metabolic rates become too high, which causes superoxides to form
-Cell needs time to adapt to environment as changes only happen gradually in nature
