29 topics with concise summaries: definitions, key facts, and classroom questions.
Microbial physiology is a branch of microbiology that studies the vital activity mechanisms of microorganisms. Here we examine how bacteria, fungi, protozoa, and viruses produce energy, grow, reproduce, and interact with host cells.
The material of this section is divided into three main blocks. The first is dedicated to cellular forms: from the chemical composition, constructive metabolism, and types of bacterial respiration to nutrient media and cultivation conditions. The second block details viral life cycles — from replication mechanisms of various genomes (retroviruses, hepadnaviruses, plus- and minus-strand RNA viruses) to integrative infection and persistence. The third block focuses on bacteriophages, the phenomena of lysogeny, and the medical applications of phages.
Classes and exams traditionally require a deep understanding of bacterial metabolic pathways (especially the differences between fermentation and respiration), the reproduction mechanisms of specific viral groups, and types of viral infection. Without this foundational knowledge, it is impossible to understand the pathogenesis of infectious diseases and the principles of antimicrobial drugs.
What will happen to a bacterial cell when water is removed?
Reproduction and metabolic reactions will stop, but the cell will not die. This principle is the basis for microbial preservation via lyophilization.
What is the fundamental difference between lithotrophs and organotrophs?
Both groups belong to chemotrophs, but lithotrophs oxidize inorganic substances (hydrogen sulfide, ammonia, iron ions) as electron donors, while organotrophs use organic compounds for this purpose.
Why is sucrose added to the medium for cultivating mycoplasmas?
Mycoplasmas and bacterial L-forms lack a rigid cell wall that protects against osmotic pressure. Sucrose creates a hypertonic environment, preventing osmotic lysis (destruction) of the cells.
Where is the respiratory chain localized in bacteria?
The process occurs on the cytoplasmic membrane and intracellular membrane structures (its derivatives), as bacteria lack mitochondria.
How does fermentation differ from respiration?
In fermentation, organic compounds act as hydrogen acceptors, and the process proceeds without oxygen. In respiration, the acceptor is an inorganic substance.
Why do strict anaerobes die in the presence of oxygen?
They lack protective enzymes (catalase and peroxidase) capable of neutralizing toxic oxidation products—hydrogen peroxide and the superoxide radical.
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