Govt Exams
Staphylococcus aureus characteristically forms clusters (not chains), produces alpha-hemolysin (alpha-toxin), and is coagulase-positive, distinguishing it from streptococci.
Flagellin comprises the helical filament and constitutes the H (Hauch) antigen, used for serotyping bacteria like Salmonella. Other flagellar components are internal and less immunogenic.
Filoviruses (Ebola, Marburg) cause hemorrhagic fevers, possess negative-sense RNA, and display characteristic helical/filamentous morphology with extreme pathogenicity.
Influenza A virus has 8 RNA segments, enabling antigenic reassortment. This segmentation allows rapid evolution and pandemic potential through genetic exchange with other influenza strains.
Mycolic acids in the mycobacterial cell wall resist acid-alcohol decolorization, causing the characteristic acid-fast staining. These long-chain fatty acids are unique to mycobacteria.
Beta-lactamase enzymatically cleaves the beta-lactam ring of penicillin, inactivating the antibiotic. This is enzymatic degradation, not target modification or pump-mediated resistance.
Bacillus and Clostridium are the primary gram-positive bacteria capable of forming endospores. These structures are highly resistant to heat, chemicals, and radiation.
Positive-sense RNA can directly serve as mRNA for ribosomal translation. Replication requires RNA-dependent RNA polymerase. This genome type doesn't undergo reverse transcription or DNA synthesis.
Pili (sex pili) mediate bacterial conjugation, enabling direct DNA transfer between cells. Flagella aid motility, capsules provide protection, and teichoic acids are cell wall components.
Pseudomonas aeruginosa is a gram-negative, oxidase-positive rod commonly causing respiratory infections in hospitalized patients. E. coli and Klebsiella are oxidase-negative, while Proteus is also oxidase-negative.