"Bacterium" - what is it, definition of the term
A bacterial cell is a microscopic, unicellular prokaryote lacking a membrane‑bound nucleus; it possesses a relatively simple internal organization, a cell wall typically composed of peptidoglycan, and reproduces chiefly through binary fission, enabling rapid population expansion under suitable conditions.
Detailed information
Bacterial microorganisms are single‑celled prokaryotes lacking a membrane‑bound nucleus. Their size typically ranges from 0.5 to 5 µm, and cell walls are composed of peptidoglycan, which determines Gram‑positive or Gram‑negative staining characteristics. Morphological forms include cocci, bacilli, spirilla, and filamentous structures; each shape reflects adaptations to specific ecological niches.
Genomic organization consists of a circular chromosome, often supplemented by plasmids that carry accessory genes such as antibiotic‑resistance determinants. Replication proceeds bidirectionally from a single origin, and transcription and translation are coupled within the cytoplasm. Metabolic pathways vary widely: some species ferment sugars anaerobically, while others oxidize organic acids aerobically, enabling survival in diverse environments.
In rodents such as rats and mice, microbial infections can manifest as gastrointestinal distress, septicemia, or respiratory disease. Notable pathogenic species include Salmonella enterica, Yersinia pestis, and Streptococcus pneumoniae. Transmission routes involve contaminated feed, water, bedding, or direct contact with infected conspecifics. Clinical signs often comprise weight loss, lethargy, and abnormal fecal consistency.
Laboratory colonies rely on defined microbial strains for research on immunology, microbiome interactions, and drug efficacy. Standard cultivation media—e.g., Luria‑Bertani broth, MacConkey agar, and blood agar—support growth under controlled temperature (30–37 °C) and atmospheric conditions (aerobic, microaerophilic, or anaerobic). Colony morphology, hemolysis patterns, and biochemical tests (oxidase, catalase, indole) assist in species identification.
Antimicrobial susceptibility testing follows Clinical and Laboratory Standards Institute guidelines, employing disk diffusion or broth microdilution methods. Resistance mechanisms encompass enzymatic drug inactivation, target modification, and efflux pump activation. Surveillance data guide therapeutic choices and inform biosecurity protocols in animal facilities.
Detection techniques include polymerase chain reaction for species‑specific gene targets, quantitative real‑time PCR for load estimation, and immunoassays for antigen identification. Whole‑genome sequencing provides comprehensive insight into virulence factors, phylogeny, and potential zoonotic threats.
Effective management of rodent‑associated microbial populations requires strict hygiene, regular health monitoring, and appropriate quarantine measures. Integration of microbiological knowledge with animal husbandry practices minimizes disease outbreaks and enhances experimental reliability.