Batterjee Medical College

Ass. Prof. Dr. Manal El Said Head of Microbiology Department Bacteria Growth and Physiology

Batterjee Medical College

Define the following: a. binary fission b. generation time c. geometric progression Learning Objectives for "Bacterial Growth" After completing this section you should be able to perform the following objectives.

Batterjee Medical College Bacteria reproduce by binary fission, a process by which one parent cell divides to form two progeny cells. Bacterial Reproduction (1)

Batterjee Medical College Bacterial Reproduction (2) Binary Fission

Batterjee Medical College Exponential growth (logarithmic growth): one cell gives rise to two progeny cells The doubling (generation) time of bacteria: It is the time it takes for a population of bacteria to double in number. It ranges from 20 minutes for Escherichia coli to more than 24 hours for Mycobacterium tuberculosis. Bacterial Growth Curve (1)

Batterjee Medical College The growth cycle of bacteria has four major phases The standard growth curve can be demonstrated: If a small number of bacteria are inoculated into a liquid nutrient medium and the bacteria are counted at frequent intervals 1- The lag phase: During which metabolic activity occurs but cells do not divide (few minutes up to many hours). 2- The log (logarithmic or Exponential ) phase: - Rapid cell division occurs. -β -Lactam drugs (e.g. penicillin) act during this phase because they are effective when cells are dividing. 3- The stationary phase: Nutrient depletion or toxic products cause growth to slow until no. of new cells balances no. of cells death resulting in a steady state. 4-The death phase: - Decline in the number of viable bacteria. Bacterial Growth Curve (2)

Batterjee Medical College Bacterial Growth Curve (3)

Batterjee Medical College

1. Define the following: a. Psychrophile b. Psychrotroph c. Mesophile d. Thermophile e. Obligate aerobe f. Obligate anaerobe g. Aerotolerant anaerobe h. Facultative anaerobe 2. State the optimum pH range for most bacteria 3. Define the following: a. Phototroph b. Chemotroph c. Autotroph d. Heterotroph e. Fastidious Learning Objectives for "Factors Influencing Bacterial Growth" After completing this section you should be able to perform the following objectives.

Batterjee Medical College Physical Requirements Factors Influencing Bacterial Growth Nutritional Requirements 1.Temperature 2.Oxygen requirements 3.PH 4.Osmosis 1- Energy source 2- Carbon source 3- Nitrogen source 4- Minerals - Sulfur - Phosphorus - Potassium, magnesium & calcium - Iron - Trace elements 5- Water 6- Growth factors

Batterjee Medical College 1-Temperature Factors Influencing Bacterial Growth: Physical Requirements DefinitionOptimum growth temperature PsychrophilesCold-loving bacteriaBetween – 5C and 15C. MesophilesBacteria that grow at moderate temperatures. Between 20C and 40C. Most bacteria are mesophilic & include soil bacteria and bacteria that live in and on the body. ThermophilesHeat-loving bacteriaBetween 45C and 70C. HyperthermophilesBacteria that grow at very high temperatures Between 70C and 110 C.

Batterjee Medical College Definition They obtain energy through Obligate aerobes Grow only in the presence of oxygenAerobic respiration Microaerophiles - Require a low concentration of oxygen (2% to 10%) for growth - Higher concentrations are inhibitory Aerobic respiration Obligate anaerobes Grow only in the absence of oxygen (inhibited or killed by its presence). - Anaerobic respiration -or fermentation Aerotolerant anaerobes (obligate fermenters ) - Cannot use oxygen to transform energy - Can grow in its presence. Only by fermentation Facultative anaerobes Most bacteria - Grow with or without oxygen - But generally better with oxygen. -Aerobic respiration if oxygen is present - Fermentation or anaerobic respiration if it is absent. 2- Oxygen requirements Factors Influencing Bacterial Growth: Physical Requirements

Batterjee Medical College 2- Oxygen requirements (2) Factors Influencing Bacterial Growth: Physical Requirements

Batterjee Medical College 3- pH Neutrophiles AcidophilesAlkaliphiles pH range of 5-8 ph 8.5 pH 5.5 Most pathogens grow at pH 7.2 = pH of blood and body tissues Factors Influencing Bacterial Growth: Physical Requirements

Batterjee Medical College Osmosis is the diffusion of water across a membrane: -From higher water concentration (lower solute concentration) -To lower water concentration (higher solute concentration) Osmosis does not require energy. 4- Osmosis (1) Factors Influencing Bacterial Growth: Physical Requirements

Batterjee Medical College Factors Influencing Bacterial Growth: Physical Requirements 4- Osmosis (2) Both the water and solute concentration are the same inside and outside the cell Water goes into & out of the cell at an equal rate. (Most bacteria) The water concentration is greater inside the cell & the solute concentration is higher outside. Water goes out of the cell. The water concentration is greater outside the cell &the solute concentration is higher inside. Water goes into the cell.

Batterjee Medical College Factors Influencing Bacterial Growth: Physical Requirements 4- Osmosis (3) Osmotolerant Organisms :can grow at high salt concentration (up to 10%). Halophiles : require high salt concentrations for growth, (up to 20% or higher ).

Batterjee Medical College They use the oxidation & reduction of chemical compounds 1- Energy Source They use sunlight to convert CO 2 & water into organic materials Factors Influencing Bacterial Growth: Nutritional Requirements (1) Phototrophs Chemotrophs Photosynthesis Respiration Fermentation

Batterjee Medical College Respiration: 1- Aerobic Respiration It is glucose catabolism under aerobic condition. This results in the production of energy in the form of 38 ATP molecules. Aerobic respiration involves : 1- Glycolysis The end product of glycolysis are: - 2 molecules of pyruvic acid - 2 ATP molecules. 2-The Krebs cycle The substrate are the 2 molecules of pyruvic acid Generating 2 ATP molecules. 3- Oxidative phosphorylation 3- Oxidative phosphorylation (Electron transport chain) It result in the formation of 34 ATP molecules. The final electron acceptor is molecular O 2

Batterjee Medical College Respiration: 2- Anaerobic Respiration It occurs in the absence of oxygen. The final electron acceptor is an organic molecule such as nitrate, sulfate or CO 2 There is also: - Glycolysis, - Krebs cycle - Oxidative phosphorylation Because nitrate, sulfate or CO 2 are not good electron acceptor as oxygen, the net yield of ATP molecules is less than it is with aerobic respiration.

Batterjee Medical College 3- Fermentation It is the process of extracting energy from the oxidation of organic compounds, such as carbohydrates, and using an endogenous electron acceptor, which is usually an organic compound. The sugar breakdown to pyruvic acid and then, to lactic acid or ethanol. It is the process by which facultative bacteria generate ATP in the absence of oxygen. There is no oxidative phosphorylation.

Batterjee Medical College Require organic forms of carbon. It cannot synthesize organic molecules from inorganic nutrients. Factors Influencing Bacterial Growth: Nutritional Requirements (2) 2- Carbon Source HeterotrophsAutotrophs Require only carbon dioxide as a carbon source. It can synthesize organic molecules from inorganic nutrients.

Batterjee Medical College Factors Influencing Bacterial Growth: Nutritional Requirements (3) 3- Nitrogen Source - Amino acids - DNA - RNA - ATP Nitrogen is needed for the synthesis of : - Nitrogen - Nitrates - Ammonia - Organic nitrogen compounds Nitrogen sources are:

Batterjee Medical College It is needed to synthesizes sulfur-containing amino acids and certain vitamins. Sulfur source : - Sulfates - Hydrogen sulfide - Sulfur-containing amino acids Factors Influencing Bacterial Growth: Nutritional Requirements (4) 4- Minerals 1. Sulfur It is needed to synthesize phospholipids, DNA, RNA & ATP. Phosphate ions are the primary source of phosphorus. 2. Phosphorus 3. Potassium, Magnesium and Calcium These are required for certain enzymes.

Batterjee Medical College Factors Influencing Bacterial Growth: Nutritional Requirements (5) 4- Minerals They are required in very minute amounts and function as cofactors (electron donors or acceptors) in enzyme reactions. They include sodium, zinc, copper, molybdenum, manganese and cobalt ions. 4. Iron -It is component of cytochromes and other enzymes. -Bacteria produce iron-binding compounds (siderophores) which capture iron by chelating it, attach to specific receptors & actively transported into the cell. 5. Trace Elements

Batterjee Medical College Factors Influencing Bacterial Growth: Nutritional Requirements (5) 5- Water & 6- Growth factors Growth factors are organic compounds such as: - Amino acids - Purines - Pyrimidines - Vitamins Cell must have them for growth but cannot synthesize itself. They having complex nutritional requirements & needing many growth factors Fastidious Organisms