Microbial Growth Factors and Media

Microbial Growth Factors

• Microbes have specific growth ranges and requirements influenced by various factors.
• Extremophiles adapt to their natural, often harsh, habitats through unique mechanisms.
• Non-extremophiles use strategies to acclimate to environmental changes.
• Microbes possess enzymes to defend against toxic oxygen products.
• Microbes employ various mechanisms to endure starvation.
• Sessile microbes attach to surfaces, while planktonic microbes float freely.
• Biofilms form in natural, industrial, and medical settings and have significant implications.
• Quorum sensing regulates cellular processes in microbes.
• Culturing microbes is crucial for studying microorganisms.

Media Types and Isolation Techniques

• Defined (synthetic) media differs from complex media in composition.
• Liquid media serves different purposes than solid growth media.
• Agar is a useful solidifying agent due to its unique characteristics.
• Supportive, enriched, selective, and differential media each have unique uses.
• Enrichment cultures help isolate microbes.
• Streak plate, spread plate, and pour plate methods isolate pure cultures.
• Microbiologists use specific terms to describe colony morphology.

Microbial Growth Curve and Population Measurement

• Microbial growth in batch cultures follows five phases.
• There are three hypotheses for cell number decline during the death phase.
• Viable but nonculturable cells in food or water can affect public health.
• Nutrient concentrations correlate with the phases of a microbial growth curve.
• Direct cell counts, viable counting, and cell mass measurements determine population size.
• Plate count results are expressed as colony-forming units (CFU).
• Approaches should be designed to measure the population size of different sample types.
• Batch and continuous cultures are distinct methods of culturing.
• Chemostats and turbidostats differ in how they maintain culture conditions.
• The dilution rate of a chemostat influences population size and growth rate.

Microbial Control

• Disinfection, antisepsis, chemotherapy, and sterilization each have distinct actions.
• "-cidal" agents kill microbes, while "-static" agents inhibit them.
• The decimal reduction time (D value) quantifies agent effectiveness.
• Antiseptics, disinfectants, and sterilization correlate with agent effectiveness.
• Heat and radiation control microorganisms through specific mechanisms.
• Filtration removes microorganisms.
• Filtration methods can selectively remove microbes from mixed populations.
• Phenolics, alcohols, halogens, heavy metals, quaternary ammonium chlorides, aldehydes, and oxides control microorganisms.
• These agents have specific mechanisms of action.
• Microbial population size & composition, temperature, exposure time, and environmental conditions affect antimicrobial agent effectiveness.
• Processes such as measuring killing rates, dilution testing, and in-use testing assess antimicrobial agents.
• Predation, competition, and other methods can biologically control microorganisms.
• Viruses of bacteria, fungi, and protozoa can provide alternative decontamination and medical therapies.
• Effective microbial removal strategies should be classified and justified.

Antimicrobial Chemotherapy

• The history of antimicrobial chemotherapy can be traced.
• Natural sources can yield new antimicrobial agents.
• Narrow-spectrum drugs differ from broad-spectrum drugs.
• Drug action correlates with "-cidal" or "-static" effects.
• Dilution susceptibility test, disk diffusion test, and the Etest determine antibacterial drug activity.
• It's possible to predict antimicrobial drug levels in vivo from in vitro data.
• Antibacterial, antifungal, antiviral, and antiprotozoan drugs each have unique mechanisms of action.
• The relative effectiveness of antibacterial agents depends on their drug target.
• There are far fewer antifungal, antiviral, and antiprotozoal agents compared to antibacterials.
• Combination drug therapy, like anti-HIV models, has a rationale.
• Side effects and toxicity of antibacterial and antiprotozoal drugs relate to their mechanisms.
• Delivery route, metabolism, and local concentration influence antimicrobial drug effectiveness.
• Microorganism sensitivity to antimicrobials relates to microbial growth.
• Microbes develop resistance to antimicrobial chemotherapeutic drugs through various mechanisms.
• Practices leading to antimicrobial drug resistance should be identified, and countermeasures suggested.