A notable property of Proteus is the ability to swarm on solid media. Discrete colonies are seen in young cultures but thereafter actively motile cells spread on the surface of plate in successive waves to form a thin layer in concentric circles.
WHY DO THE PROTEUS SWARM ?
Swarming takes place in a discontinuous manner each period of outward progress followed by a stationary period.
# multinucleate cells (swarm cells) synthesis numerous number of flagella
# acidic polysaccharide slime helps in swarming
# negative chemotactic factors accumulate during growth
# moisture on agar surface
swarming growth is a problem in the laboratory when mixed growth is obtained in which Proteus bacilli overgrown with other bacteria.
METHODS TO PREVENT SWARMING:
Several methods have been devised to inhibit swarming of Proteus.
1. AGENTS WHICH ALTER GROWTH CHARACTERISTICS:
Ø Bile salts in Mac Conkey agar inhibits growth of Proteus
Ø Sodium azide in a concentration of about 1:500- inhibits growth
2. INHIBITION OF MOTILITY:
Ø Increase in concentration of agar upto 6% inhibits migration of Proteus and consequently isolated colonies are formed.
Ø 0.02% tannic acid –tannic acid binds to outer membrane of cell wall inhibiting the movement of flagella.
Ø 20mM salicylate decreases motility of Proteus.
3. AGENTS WHICH ACT ON FLAGELLA PRODUCTION:
Ø Incorporation of Boric acid – 1:1000 form complex with flagellin and cause disintegration of flagella. Thus inhibiting migration and prevent swarming.
Ø 1x106 Plaque forming units/ml – Phage X7 is a flagellotropic phage for Proteus.
Ø The addition of 0.2 ml of phage spread over the surface of agar plates and immediately immobilizes the Proteus.
Ø In fish meal extract agar with NaCl swarm cells were not formed due to deficiency of glutathione, viscous environment and flagella rotation inhibition.
Ø Effect of sodium tetradecyl sulfate immobilizes the strain by inhibition of flagella formation or by some lytic action on flagella.
Ø Phenyl ethyl alcohol – concentration of 5 to 6% impairs flagella function but leaves the flagellum morphologically intact.
Ø Addition of ferrous salts to protease peptone medium inhibits flagellar function without affecting growth of the organism.
4. DEFICIENCY OF ELECTROLYTES:
Ø Cystine Lactose Electrolyte Deficient medium (CLED) – peptone base agar with lactose and L-cystine restriction of electrolytes inhibits swarming of Proteus.
5. OTHERS WHICH PREVENT SWARMING:
Ø Media containing activated charcoal (1% w/v charcoal in nutrient agar base) inhibits swarming but not the growth of Proteus. The suppression depends on the concentration of charcoal in medium. It does not interfere with flagella production.
Ø Chloral hydrate and Sulphonamide inhibits swarming when added to media.
Ø Predried plates with para nitro phenyl glycerine inhibits swarming without imparing motility. It has long shelf life, heat stable and convenient to use in preparation of media.
Ø Sodium desoxycholate - Leifson BD desoxycholate agar prevents swarming
Ø Anionic detergents such as sodium alkyl sulfate in concentration of 0.1m mol/L without affecting its growth
Ø Selective Proteeae medium (SPM) contains tryptose phosphate agar, phenolphthalein monophosphate, bile salts and polymixin B – inhibits swarming.
Ø Bismuth Sulphite in Wilson Blair medium.
Ø Use of monopterenes (terpenes & terpenoids) and psychotropic drugs (serotonin & sertalin) inhibit swarming of Proteus.
- Ms. Sweetha & Ms. Subha
Keywords: Proteus, Swarming motility, Proteus mirabilis, Proteus vulgaris, Swarming Proteus