1. Bacterial growth requires nutrients, an appropriate temperature range, and specific gas conditions. Growth occurs in phases including a lag phase, logarithmic phase of rapid cell division, stationary phase, and death phase. 2. Many factors influence bacterial growth rate, including the type and concentration of nutrients, pH, temperature, and ionic strength of the environment. 3. Bacteria metabolize through anabolic and catabolic pathways using various modes of energy production such as aerobic respiration, anaerobic respiration, and fermentation. Metabolites and energy storage compounds support these metabolic processes. 4. Methods to determine bacterial numbers include total counts of live and dead cells as well as viable counts of only live cells

1. Bacterial growth
Almugadam B Saad
Lecturer of medical microbiology
Faculty of medical laboratory sciences
Full name
Babiker Saad Almugadam YousifFaculty of medical laboratory sciences
University of El Imam El Mahadi
Kosti-Sudan
MSc University of Khartoum
BSc University of El Imam El Mahadi
Babiker Saad Almugadam Yousif

2. Bacterial growth
- Growth requirement
- Growth curve
- Factor affect growth and growth rate
Learning
objectives
- Factor affect growth and growth rate
- Metabolism
- Bacterial count

3. Growth requirement
- Include the following:
A- Nutritional requirements :
- Include Main nutritional components : C , H , N2 , O2 , P , S
Others : mg , K , Fe, Ca, Zn , Co , Cu , mn
Macronutrients : need in large amount as
A- Nutritional B- Temperature
C- Gasses atmosphere D- Humidity
Macronutrients : need in large amount as
- Also distributed into P, K ,S , Mg , Na , Fe++ ,
Micronutrients : need in small amount as
Zn+ , Vitamins , Ca++
- Source of carbon : Organic CHO , AA , Lipid
- Source of nitrogen : Organic in form of nitrate or nitrites
Inorganic some bacteria can fix
atmospheric N2 and others use NH4+ salt

4. B- Temperature :
Temperature has direct effect on growth , and viability of organisms.
The temperature at which a microorganism grows best is referred to
as its optimum temperature. The temperature below which growth
stops (inhibited) is called the minimum temperature,The temperature
above which growth stops and death occurs is called the maximum
temperature. Each degree of temperature required is provide bytemperature. Each degree of temperature required is provide by
incubator .
Each organism has Optimum , minimum ,
and maximum temperature.
The temperature used for routine culturing
is 35–37Co

5. Bacteria classify according to temperature of growth for:
1.Thermophilic ?
2.Hyperthermophilic ?
3.Mesophilic ?
4.psychrophiles ?
5. psychrotrophs
Incubator

6. C- Gasses atmosphere :
-According to gasses atmosphere , bacteria classify into
Obligate aerobic : grow only in presence of O2
Obligate anaerobic : grow only in absence of O2
Facultative anaerobic : grow in presence or absence of O2
Aerotolerant anaerobes : tolerate the presence of oxygen but
not require it for growthnot require it for growth
Micro-aerophilic : require atmosphere with 5% O2 and 10% Co2
Carboxyphilic : require Co2 enriched atmosphere
D- Humidity :
-Dry atmosphere can affect the growth and viability of many
pathogens. Inclusion of a piece of damp blotting paper in the
bottom of jar is recommended for the culture of these pathogen.

7. Growth curve
- Bacteria reproduce by binary fission
- Doubling time (Generation time) : time required by bacteria to
divide , as little as 20 min for E.coli and as long as 18h for
M.tuberculosis
- Number of bacteria after many generation :
Rule : Nn= 2NonRule : Nn= 2Non
N= number of cell n= number of generation
No= number of cell before generation
- Growth phase :
Bacteria during their growth path through 4 phase called growth
phase , include : Lag , Log , Stationary , Decline phase.

8. 1- Lag phase : during which vigorous metabolic activity occur,
growth rate zero .
2- Log phase (Logarithmic , Exponential) : rapid cell division ,
growth rate reach constant maximum value.
- Diauxic growth (Diauxy) : characterized by 2 log phase separated
by lag phase , occur in presence of 2 different carbon sources
- Maintaince of microbe in log phase : by using of continuous
culture systems(in which nutrients continuously added and wasteculture systems(in which nutrients continuously added and waste
continously removed). Types ?
continuous culture systems Aim of use ?
Difficulties ?
3- Stationary phase : There is steady state as result of balance
between new generated cell and died cell , growth rate fall zero
4- Decline phase (Death) : decline in number of viable cells

10. Factor affect growth
- Many include :
1- Genetic constitution 2- Environmental factor
3- Age of cell 4- Competition
Factor affect growth rate
- Include :- Include :
A- Nature and concentration of nutrient B- pH
C- Temperature D- Ionic strength

11. Metabolism
- Chemical reaction occur in living cell , include 2 process :
Anabolism : energy require
Catabolism : energy liberate
- Metabolites : Precursor products of metabolism
- Product : can not go further metabolized
- Energy storage compounds include : ATP , Thioesters ,- Energy storage compounds include : ATP , Thioesters ,
acylphosphates
, guaridine phosphate and phosphoenolpyruvate.
- Mode of energy yielding :
A. Respiration : occur by aerobic or anaerobic oxidation
In aerobic oxidation : in which organic or reduced inorganic
compound serve as electron donor and molecular oxygen as
electron acceptor .

12. In anaerobic oxidation : in which organic or reduced inorganic
compound serve as electron donor and oxidized inorganic
compound other than oxygen serve as electron acceptor , such
as sulfate or nitrate or CHO .
B. Fermentation : in which organic compound serve as electron
donor and acceptor , occur under strict anaerobic condition
, CHO are principle substrate. Fermentation of sugar ?, CHO are principle substrate. Fermentation of sugar ?
C. Photosynthesis : Use light as source of energy , occur under
strict anaerobic condition.

13. Bacterial count
-Methods of total count : Dead and live
1-Tubidimetery and nephelometry 2- Dry weight
3- Cell packing by centrifugation 4- N2 determination
5- Analysis of substrates and end products 6- Coulter counter
7- Analysis of other cellular 8- Microscopic determination
components of cell numberscomponents of cell numbers
-Methods of viable count : Live only
1- Drop-plate 2-Pour-plate (deep plate) 3- Roll-tube
4- Surface spread 5- Shake culture 6- Spore counts
7- Most probable number (MPN)method
-Errors of counting :
1- Dilution errors 2- Sampling errors 3- Counting errors
4- Random variation errors 5- Influence of environmental factor