Microbial Nutrient Requirements and Resistance Mechanisms

What Nutrients Do Microbes Need for Growth?

Macronutrients to build macromolecules: carbon, nitrogen, phosphorus, sulfur, oxygen. Various micronutrients are also required by microbes, including several metal ions (cations) like K+, Na+, Mg2+, Ca2+, Fe2+ or Fe3+, Mn2+. Prototrophs synthesize nutrients from inorganic material, while auxotrophs require additional nutrients. Aerobic microbes need oxygen, while anaerobic ones do not. pH and osmotic pressure also affect microbial growth. Different types of media and methods like streak plate, spread plate, and pour plate are used for microbial culture. Antibiotics interfere with various microbial processes like peptidoglycan synthesis, membrane integrity, DNA synthesis, and ribosome function.

How Do Microbes Become Resistant?

Adaptation to selective pressures drives genetic changes in microbes. Drug resistance genetic changes are negative. Mechanisms of resistance include β-lactamase production, alteration of penicillin-binding proteins, and reduction of membrane permeability to drugs.

Microbial Motilities and Gene Expression

Flagella, fimbriae, pili, and secretion systems play a role in bacterial motility. Type three secretion systems (T3SS) are important for bacterial pathogenicity. Studies on Pseudomonas fluorescens C7R12 show unique extracellular structures like polar flagella, thin flexible pili, and fimfria-like appendages.