3 Pages
Unlock Document

Biological Sciences
Malcolm Mac Kinnon

Bacteria (single celled, prokaryotic)  Only small number are pathogens  Asexually reproduction by binary fission / 2 identical daughter cells  Grow best at optimum conditions (human body) o Constant temperature o Neutral pH o Constant supply of food, H2O, O2 o Mechanism removing waste  Most bacteria are aerobic / obligated aerobes  Aerobic bacteria growing with absent oxygen / facultative anaerobes  Bacteria which find oxygen toxic / obligate anaerobes Sigmoid growth curve shows the number of bacteria plotted against time  Bacteria MUST grow in closed system and nutrient medium → BACTERIAL CULTURE o 1) Population grows slowly - LAG PHASE o 2) Rapid increase of population growth - LOG PHASE o 3) Reaches equilibrium when number remains constant - STATIONARY PHASE  Lag Phase → initial phase o Low number of reproducing organisms o Bacteria increase in size before division o This requires nutrients which need to be digested o Digestion requires enzymes, proteins → activation of genes → time consuming process  Log Phase → exponential phase; max growth rate; steep curve o Optimum conditions: no limiting factors, waste does not accumulate to a toxic level o Bacteria most susceptible due to production of new cells  Antibiotics inhibit cell wall formation  Antibiotics inhibit DNA replication  Antibiotics inhibit protein synthesis  Stationary Phase → reduced growth rate o New cell production balanced by death of cells o Limiting factors, declining nutrients, accumulating waste influence population size  Decline Phase → bacteria stop dividing o Death rate increases; numbers may fall to zero o Lack of nutrients, build up of toxic waste products  Aseptic conditions o Sterilise equipment, instruments, thus, to prevent contamination with the culture. o Use high temp and disinfectants Total cell count  Number of cells whether living or dead  Count cells with haemocytometer  Stop bacteria entering the flask with a stopper. Important as bacteria would have been caused reduced growth rate of yeast/killed yeast and competed for space/nutrients  Culture is shaken to achieve a uniform distribution of yeast cells/spread out yeast  Larger number is taken to avoid anomalies/produce an average Measurement of growth Generation time: time taken for a bacterial population to double  Rate of population o = increase in number of yeast cells/time o = number larger - number less/(time larger - time less)  Suppose the number of cells in one square are 6 8 9 5 7  The sum of the cells in 5 squares is 35
More Less

Related notes for BIOC31H3

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.