Variable Ammonia Production Among Smooth and Rough Strains of Pseudomonas pseudomallei : Resemblance to Bacteriocin Production

Abstract

The colonial morphology of some strains of Pseudomonas pseudomallei was correlated with certain biochemical and physiological traits. After 3 days of growth on Wahba or heart infusion agars, smooth-colony strains generated toxic amounts of ammonia. Under the same conditions, the rough strains simultaneously produced oxalic acid which decreased the inhibitory concentration of ammonia. The ammonia-ammonium concentrations in smooth cultures exhibited certain bacteriocin-like characteristics. An unusually stable, smooth strain (strain 165) was chosen to compare and emphasize any differences with typical, rough strain 7815. Three-day-old smooth cultures grown on Wahba agar containing 3% (w/v) glycerol demonstrated ammonia toxicity. The substitution of glucose for glycerol completely obviated this toxicity. In highly aerated Wahba broth containing glucose, the amount of ammonia found in strain 165 smooth cultures and the amount of oxalic acid found in strain 7815 rough cultures were greatly reduced. In Difco nitrate broth smooth strain 165 did not form gas, and it reduced nitrate to nitrite only. Strain 7815 produced a gas and reduced both nitrate and nitrite. Antibiosis among bacterial strains is a common occurrence and is sometimes useful as an aid in laboratory identification. One of the most striking antagonisms in this respect is attributed to a class of compounds called bacteriocins. The bacteriocins are generally defined as protein-like, naturally occurring bacterial antibiotics which act principally on strains of the same species as the producer or on genetically related species. Some bacteriocins act on species of other genera (4, 25). Our efforts to find bacteriocins among strains of Pseudomonas pseudomallei proved fruitless. However, another type of antagonism was found which resembled bacteriocin antibiosis, but was essentially due to ammonia excretion. This paper describes the conditions under which ammonia toxicity was observed and some interesting correlations among colonial morphology, physiological and genetic traits. MATERIALS AND METHODS Strains and cultural conditions. Eighteen isolates of P. pseudomallei were obtained from water, soil, and animal sources in Vietnam, Malaysia, and Thailand. P. mallei (synonym Actinobacillus mallei, strains 4 and 3873) and P. cepacia (synonym P. multivorans, strains 17616 and 17759) were described previously (26). P. aeruginosa pyocin indicator strains were obtained from R. J. Zabransky (38). Strains were maintained on Difco brain heart infusion agar containing 3% (w/v) glycerol (glycerol agar). Survey for inhibiting strains. The survey procedures were essentially those of Darrell and Wahba (6), except that the basal medium (36) was heart infusion broth (Difco) containing 10-6 M iodoacetic acid, 0.1% sodium citrate, 0.1% K2HPO4, 0.0018% phenol red dye, and 2% agar (Wahba agar). In the survey, a candidate inhibitor strain was streaked on Wahba agar and incubated at 37 C for 3 days. The cultures were then exposed to CHClI vapors for 30 min, the growth was scraped off w...

Description of a bacteriocinogenic plasmid in Beneckea harveyi

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Colicinogeny and related phenomena.

“…On turning to other groups of bacteria, and particularly to gram-positive genera, the inhibition zones seen on agar plates are more likely to be due to various unrelated inhibitors. The results of surveys which measure the incidence of "bacteriocinogeny" in bacteria other than members of the Enterobacteriaceae are particularly difficult to assess in view of the reports of bacte-riocin-like action due to such diverse agents as ammonia (482), hydrogen peroxide (264,389), lactic acid (567), phospholipases (including clostridial a-toxin) (114,455), hemolysins (58,259), the lytic enzyme lysostaphin (501), bacteriophage tails or defective bacteriophages (49,142,298,308,496), phospholipids, and fatty acids (580).…”

Properties of a Streptococcus sanguis (Group H) Bacteriocin and Its Separation from the Competence Factor of Transformation

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