GROWTH CURVE.pdf

PG AND RESEARCH DEPARTMENT OF MICROBIOLOGY,SRI PARAMAKALYANI COLLEGE, ALWARKURUCHI-627 412

1. Reaacreditedwith B grade with a CGPA of 2.71 in the second cycle of NAAC
affiliated to manomaniumsundaranaruniversity, Tirunelveli.
Post graduate & Research Centre –Department of
Microbiology
(government aided)
I SEMCORE: MICROBIALPHYSIOLOGY AND METABOLISM
(ZMBM13)
UNIT-5
BACTERIAL GROWTH CURVE
S. SARAL BEEVI SUBMITTED TO
REG.NO:20211232516123 GUIDE :DR. VISWANATHAN. PH.D.,
I. M. SC. MICROBIOLOGY ASSISTANT PROFESSOR AND HEAD
ASSIGNED ON : 05/12/2022 SPKC ALWARKURCHI
TAKENON : 12/01/2022

2. INTRODUCTION
GROWTH CURVE-FOUR PHASES
LAG PHASE
LOGPHASE
LIMITATIONS OF LOG PHASE
STATIONARY PHASE
DEATH PHASE
MATHEMETICAL CALCULATIONS OF GROWTH
CURVE OF BACTERIA
CALCULATION OF GENERATION TIME
EXAMPLE
REFERENCES

3. Bacterialgrowthisregulatedbynutritional
environment.
Whensuitableenvironmentistherethattimebacterium
isincubated,itsgrowthleadstoincreaseinnumberof
cellswhichallowdefinitecourse.

4. Thegrowthcurvehasgotfourphases:
Lagphase
Logphaseorexponentialphase
Stationaryphase
Declinephase

5. LAG PHASE(1-4 HOUR)
➢Bacteriaadaptthemselvestogrowthconditions.Itis
theperiodwheretheindividualbacteriaarematuring
andnotyetabletodivide.
➢Duringthelagphaseofthebacterialgrowthcycle,
synthesisofRNA,enzymes,andothermolecules
occurs.
➢Lengthofthisphasedependontypeofbacterial
species,culturemedium,andenvironmentalfactors.

7. It is a period characterized by cell doubling. The number of new
bacteria appearing per unit time is proportional to the present
population.
The rate of cell division is currently at its maximum with the
number of bacteria doubling as often as every 20 minutes.
Exponential growth is balanced growth .i.e., all cellular
constituents are manufactured at constant rates relative to each
other.
The population is most uniform in terms of chemical and
physiological propertiesduring this phase; therefore log phase
cultures are usually used in biochemical and physiological
studies.

9. Limitations of log phase:
Exhaustion of nutrition
Accumulation of toxic metabolites and products
Rise in cell density
Change in PH.
(Log phase is the time when cells are most active
Metabolicallyandispreferredforindustrial
purpose)

10. The rate of growth levels stop during this
period.
This is because:
❑The nutrients are becoming used up
❑The amount of waste produced by the bacteria
themselves is increasing.
❑The rate at which new cells are produced is
equal to the rate at which other cells are dying.

12. During this phase more bacteria are dying than
are being produced. This is because:
•Very few nutrients are left
•Many bacteria are poisoned by the waste
produced by such large numbers.
•Finally, after certain time period all the cells
die and culture becomes sterile.

13. Generation time-Doubling time
During the exponential phase each
microorganism is dividing at constant
intervals.
Thus the population will double in number
during a specific length of timecalled the
generation time or doubling time.

14. G(generationtime)=(time,inminutesor
hours)/n(numberofgenerations)
G=t/n
t=timeintervalinhoursorminutes
B=numberofbacteriaatthebeginningofatime
interval
b=numberofbacteriaattheendofthetimeinterval
n=numberofgenerations(numberoftimesthecell
populationdoublesduringthetimeinterval)

15. b = B x 2
n
(This equation is an expression of growth by binary
fission)
Solve for n:
Log b = log B + n log2 ; n Log2 = log b –log B
n =log b –log B
log2
( The value of log 2 is 0.301 & log b –log B = log b/B )
n =log b –log B ; n = 1 log (b/B)
0 .301 0.301
n = 3.3 log b/B
G = t/n
Solve for G
G =t/(3.3 log b/B)

17. b = 10⁷; B = 10⁴ ; t = 240 minutes
G =t/(3.3 log b/B)
G =240 minutes
3.3 log 10
7
/10
4
G = 240 minutes
3.3log10³
G=240minutes ;G=240minutes
3.3x3 (Log10³=3)
9.9
G = 24 minutes
Therefore, generation or doubling time is 24 minutes

18. 1.Prescott’s Microbiology
2.Microbiology Principles and Explorations-Jacquelyn
G. Black.
3.www.microbenotes.com
4.www.biologydictionary.net
5.www.microbeonline.com

22. Communication skill is developed.
Confidence level is increased.
Searching capability is increased.
Gained subject knowledge better.
Presentation skills are improved.
Learn the time management.