Which organism grows in alkaline pH?

Ans. is 'a' i.e., Vibrio VIBRIO CHOI.ERAEo MorphologyGram negativeBacilliNon capsulatedComma shapedS-shaped or spiral form may be seen.Arranged in parallel rows - Fish in stream appearanceMotile by polar flegellum - Darting type motility.Actively motile vibrios suggest a 'Swarm of gnats'o Culture characteristicStrongly aerobic (obligate aerobe)# Growth is better in alkaline medium (pH 6-4-9.6)0.5-1% Nacl is required for optimal growth.MaConkevs agar -->> Initial colourless colonies, later become reddish due to late lactose fermentation.Blood agar -->> Initially sorrounded by a zone of greening, which later become clear due to hemodigestion.In gelatin stab culture, infundibuliform (funnel shaped) or napiform (turnip shaped) liquefaction occur.Remembero While 0.5-1% NaCl is required for optimal growth. 6% or above NaCl inhibits the growth.Cholera toxino V. cholerae produces cholera toxin, the model for enterotoxins. whose action on the mucosal epithelium is responsible for the characteristic diarrhoea of the cholera.o Cholera toxin is a protein complex made up of six subunits -->> a single copy of 'A' subunit (Port A) and five copies of'B' subunit (Part B). 'A' subunit has two fragments; A1 and A2.o cAMP inhibits the absorptive sodium transport system (decreases sodium & chloride reabsorption) and activates the secretory chloride transport system (increases chloride and bicarbonate secretion),o This leads to accumulation of sodium choride in the intestinal lumen.o Accumulated sodium chloride draws water into the lumen due to increased osmolality leading to watery diarrhoea.