Bacterial Growth, Nutrition, and Culturing Techniques

Microbial Growth

Increase in microbial cell numbers over time.

Biofilms

Communities of bacteria adhering to surfaces.

Cultured Bacteria

Bacteria isolated and grown in laboratory conditions.

Pathogens

Microbes that cause disease in hosts.

Escherichia coli

Bacterium capable of dividing every 20-30 minutes.

Limiting Nutrients

Nutrients that restrict bacterial population growth.

Chemically Defined Medium

Minimal medium with precise nutrient composition.

Fastidious Organisms

Microbes requiring specific growth factors from environment.

H. influenzae

Requires NAD and heme to grow.

Pure Culture

Genetically homogeneous strain of a single species.

Agar

Solidifying agent derived from seaweed for cultures.

Isolation Streaking

Technique to dilute cells on agar surface.

Spread Plate

Technique for isolating colonies from liquid culture.

Colony Forming Unit (CFU)

One colony represents one viable organism.

Synthetic Medium

Contains precise amounts of basic nutrients.

Complex Medium

Nutrient-rich but poorly defined composition.

Enriched Medium

Contains blood components for fastidious organisms.

Selective Media

Promotes growth of specific organisms over others.

Differential Media

Reveals biochemical differences between species.

MacConkey Agar

Selective and differential medium for gram-negative bacteria.

Binary Fission

Asexual reproduction method in bacteria.

Budding

Asymmetrical reproduction method in some bacteria.

Asymmetrical Budding

Division method in marine bacterium Hyphomicrobium.

Exponential Growth

Population doubles at a fixed rate.

Generation Time

Time interval for bacterial cell division.

Exponential Curve

Graphical representation of population growth over time.

Nutrient Depletion

Limited resources slow bacterial growth rate.

Toxic By-products

Waste products that inhibit further bacterial growth.

Bacterial Growth Curve

Graph showing phases of bacterial population growth.

Chemostats

Our bodies act as controlled environments for microbes.

Extremophiles

Organisms thriving in extreme environmental conditions.

Temperature Extremes

Microbes' growth temperature matches their environment.

Optimum Temperature

Ideal temperature for maximum microbial growth.

Psychrophiles

Bacteria growing at 0°C, optimum at 14°C.

Mesophiles

Bacteria thriving between 20-40°C, with limits 15-45°C.

Thermophiles

Bacteria adapted to high temperatures, above 55°C.

Hyperthermophiles

Bacteria growing at temperatures up to 121°C.

Water Activity

Measure of water availability for microbial growth.

Osmolarity

Concentration of solute molecules in a solution.

pH Influence

Hydrogen ion concentration affects microbial growth.

Homeostasis

Maintaining stable internal pH in microbes.

Aerobes

Bacteria that require oxygen for energy extraction.

Anaerobes

Bacteria that cannot tolerate oxygen, often pathogenic.

Strict aerobes

Require oxygen for growth and metabolism.

Strict anaerobes

Cannot survive exposure to oxygen.

Reactive oxygen species (ROS)

Toxic oxygen molecules harming anaerobes.

Superoxide dismutase

Enzyme that removes superoxide radicals.

Peroxidase

Enzyme that removes hydrogen peroxide.

Catalase

Enzyme that converts hydrogen peroxide to water.

Facultative anaerobes

Can use oxygen or fermentation for energy.

Aerotolerant anaerobes

Only use fermentation but detoxify ROS.

Microaerophiles

Grow at low oxygen concentrations only.

Biofilm

Mass of bacteria adhering to surfaces.

Planktonic cells

Free-living cells not attached to surfaces.

Cystic fibrosis (CF)

Genetic disorder causing thick mucus in lungs.

P. aeruginosa

Bacteria often fatal in cystic fibrosis patients.

Quorum sensing

Chemical communication among bacteria in biofilms.

Sporulation

Process of forming dormant spores.

Endospores

Heat-resistant spores from certain bacteria.

Vegetative state

Active growth phase of bacteria.

Germination

Process of a spore becoming a vegetative cell.

Biofilm formation

Bacteria attach and multiply on surfaces.

Environmental stress

Conditions that threaten bacterial survival.

Communication in biofilms

Cells send signals to coordinate behavior.

Biofilm resistance

Biofilms protect bacteria from antibiotics.