Govt Exams
Proteus mirabilis produces urease, alkalinizing urine and promoting precipitation of magnesium ammonium phosphate (struvite), forming characteristic staghorn calculi.
Attachment proteins (like hemagglutinin in influenza, spike protein in SARS-CoV-2) mediate receptor binding and are immunodominant targets for neutralizing antibodies.
ESBL-producing Gram-negative bacteria (E. coli, Klebsiella) hydrolyze third-generation cephalosporins, conferring resistance to multiple beta-lactam antibiotics.
Coronaviruses are characterized by crown-like spike proteins (S protein) on their enveloped surface, which are distinctive under electron microscopy.
Bacillus cereus produces heat-resistant spores surviving cooking temperatures, causing emetic and diarrheal foodborne illness outbreaks.
Negative-sense RNA viruses (-ssRNA) cannot be directly translated; they require RNA-dependent RNA polymerase to synthesize complementary positive-sense mRNA first.
Antigenic drift (point mutations) and antigenic shift (reassortment of gene segments) allow influenza to escape previously acquired immunity, making vaccination necessary annually.
Monotrichous bacteria have a single flagellum at one pole, enabling direct, efficient movement. Peritrichous flagella around the cell body create tumbling motion.
Pseudomonas aeruginosa is a non-fermentative, oxidase-positive, Gram-negative rod commonly associated with respiratory infections and shows characteristic green pigmentation.
Gram-positive bacteria have a thick peptidoglycan layer (20-80 nm) with teichoic acids that retains the crystal violet-iodine complex, resulting in purple coloration.