Extracellular slime associated with Proteus mirabilis during swarming.

Light microscopy, transmission electron microscopy, and scanning electron microscopy were used to visualize the extracellular slime of Proteus mirabilis swarm cells. Slime was observed with phase-contrast microscopy after fixation in hot sulfuric acid-sodium borate. Ruthenium red was used to stain slime for transmission electron microscopy. Copious quantities of extracellular slime were observed surrounding swarm cells; the slime appeared to provide a matrix through which the cells could migrate. Swarm cells were always found embedded in slime. These observations support the argument that swarming of P. mirabilis is associated with the production of large quantities of extracellular slime. Examination of nonswarming mutants of P. mirabilis revealed that a number of morphological changes, including cell elongation and increased flagellum synthesis, were required for swarm cell migration. It is still unclear whether extracellular slime production also is required for migration.

Bacterial metabolism under conditions representing pesticide disposal pits.

Bacterial cultures were incubated with pesticides at concentrations ranging from 1 to 5,000 ppm. The species selected are important in one or more of the following biogeochemical processes: nitrogen fixation, nitrification, denitrification, sulfur oxidation, sulfate reduction, carbon dioxide fixation, and respiratory carbon dioxide evolution. The pesticides used were atrazine, alachlor, carbaryl, parathion, trifluralin, and 2,4-D. Bacterial cultures were exposed to commercial formulations of these pesticides and to pesticide samples from active disposal pits.

Immunofluorescent evidence of Proteus mirabilis swarm cell formation on sterilized rat feces.

Swarming Proteus spp. were detected with the use of proteometry (a most-probable-number technique) in the fecal material of selected animal species and in raw sewage from a local sewage treatment plant. Proteus spp. were not detected in any of several soil and freshwater samples examined. Since rat feces harbored high numbers of Proteus mirabilis compared with other habitats examined, we chose to examine it for the possibility of supporting swarming. Immunofluorescent studies with a strain-specific conjugate revealed the morphogenesis of short forms into elongated swarm cells upon the surface of sterilized rat feces that had been inoculated with short forms of P. mirabilis. the same phenomenon was not observed consistently when nonsterile rat feces were inoculated and examined with immunofluorescence.

Effect of salicylamide and acetaminophen on dextromethorphan hydrobromide metabolism: possible pharmacological implications.

The effect of salicylamide and acetaminophen on the metabolic fate of dextrorphan, the primary metabolite of dextromethorphan, was studied in vivo in the rat. Plasma dextrorphan levels were measured at 5-min intervals up to 20 min and at longer intervals up to 2 hr after dextromethorphan hydrobromide was administered orally either alone or in combination with salicylamide and acetaminophen. The combination gave rise to higher plasma dextrorphan levels than did dextromethorphan hydrobromide alone at most sampling times. Conjugation of dextrorphan was inhibited almost quantitatively by salicylamide and acetaminophen at the 5-min sampling time. Salicylamide alone increased the plasma dextrorphan levels when it was coadministered with dextromethorphan, but the differences were not statistically significant. The antitussive activity of dextromethorphan hydrobromide in the unanesthetized dog was faster in onset, greater in intensity, and longer in duration when it was coadministered with salicylamide and acetaminophen. It is suggested that salicylamide and acetaminophen may inhibit the metabolic inactivation of dextrorphan, thereby improving the coughinhibiting potential of dextromethorphan hydrobromide.

Determination of dextrorphan in plasma and evaluation of bioavailability of dextromethorphan hydrobromide in humans.

A method is described for the estimation of dextrorphan, a metabolite of dextromethorphan, in plasma. The bioavailability of dextromethorphan hydrobromide after 30 mg po, as measured by the concentration of total (free and conjugated) dextrorphan in the plasma, was determined in six human volunteers with this procedure.

Survival value of chemotaxis in mixed cultures.

A motile, chemotactic strain of Proteus mirabilis outgrew a motile, non-chemotactic mutant in a semisolid, amino acid medium, although the two strains grew equally well in broth.

Growth inhibition of Proteus mirabilis by cyclic adenosine 3'-5'-monophosphate.

Growth of Proteus mirabilis on a synthetic agar medium containing either glycerol, galactose, or trehalose as the sole source is inhibited by 5 mM cyclic adenosine 3',5'-monophosphate (cAMP). Inhibition on an agar medium is evident as loss of viability, but in broth cAMP only slightly inhibits growth rate. Inhibition is associated with the accumulation of methylglyoxal in the medium. A nonswarming mutant of P. mirabilis is not inhibited by cAMP on either of the three carbon sources, but it is sensitive to exogenous methylglyoxal.

Evidence against the involvement of chemotaxis in swarming of Proteus mirabilis.

Nonswarming and nonchemotactic mutants of Proteus mirabilis were isolated after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine or ultraviolet light. These mutants were used in experiments to determine if chemotaxis is involved in the swarming of P. mirabilis. Nonchemotactic mutants failed to form chemotactic bands in a semisolid casein hydrolysate medium, yet they swarmed on the same medium containing 1.5% agar. Nonswarming mutants were attracted towards individual amino acids and components of tryptose. In cross-feeding experiments, no evidence was obtained to indicate the production of a diffusable chemical repellent. In studies with the wild-type P. mirabilis, no clear-cut negative chemotaxis was seen even though three different assays were used and numerous chemicals were tested. Additional evidence against the involvement of chemotaxis in swarming comes from finding that dialysis does not interfere with swarming; swarm cells will swarm immediately when transferred to fresh media, and swarm cells will swarm on an agar-water medium supplemented with a surfactant. These data indicate that chemotaxis is not involved in the swarming of P. mirabilis.

Sulfonamide resistance of propionibacteria: nutrition and transport.

Three variations of a synthetic growth medium were used to study the folic acid and p-aminobenzoic acid (PABA) requirements of Propionibacterium. P. shermanii, P. freudenreichii, P. thoenii, and P. arabinosum synthesize folic acid and do not require PABA or folic acid. P. pentosaceum, P. jensenii, and P. rubrum are stimulated by folic acid or PABA, but do not show an absolute requirement. P. peterssonii shows a requirement for either PABA or folic acid. The addition of 300 mug of sulfadiazine per ml did not inhibit growth of propionibacteria in the synthetic medium, synthetic medium plus PABA, or synthetic medium plus folic acid. P. freudenreichii was not inhibited even when 500 mug of sulfadiazine per ml was added to the synthetic medium, nor did it degrade sulfadiazine significantly. Trimethoprim totally inhibited the growth of Propionibacterium. Radioactive sulfadiazine was transported by sulfadiazine-sensitive Escherichia coli but not by P. freudenreichii, indicating that the sulfadiazine resistance of propionibacteria could be mainly due to their inability to transport sulfonamides.

Abolition of swarming of Proteus by p-nitrophenyl glycerin: general properties.

Para-nitrophenyl glycerin (PNPG) was shown to be an effective agent to abolish the swarming of Proteus mirabilis and Proteus vulgaris on predried solid culture media. The level required to abolish swarming varied with the strain of Proteus, the components of the medium, and also with the conditions of incubation. Generally 0.1 to 0.2 mM PNPG effectively abolished swarming for at least 24 h with aerobic incubation. Levels of PNPG that abolished swarming showed no effect upon the growth of the cells, little or no effect upon the motility characteristics of the organisms, and no effect upon the cellular morphology. PNPG was found to be freely water soluble, stable to autoclaving, and to retain biological activity for at least one month in prepared culture media stored under refrigeration.

Abolition of swarming of Proteus by p-nitrophenyl glycerin: application to blood agar media.

Comparative plate counts were made of Staphylococcus aureus and Streptococcus pyogenes growing on blood agar supplemented with individual chemicals to abolish the swarming of Proteus. B-phenylethanol, sodium azide, and p-nitrophenyl glycerin (PNPG) were used as anti-swarm agents. Each anti-swarm agent effectively abolished swarming for 24 h, but azide failed to control swarming for longer periods of incubation. In addition, azide displayed growth inhibition towards the staphylococci and streptococci resulting in no hemolysis and reduced viable cell numbers with the streptococci. Phenylethanol showed reduced viable cell numbers with the streptococci and unreliable hemolytic reactions. At 0.1 to 0.3 mM, PNPG proved to be a superior anti-swarm agent in that it showed no growth inhibition and allowed normal hemolysis, but abolished swarming for extended periods of time. When laboratory strains of Streptococcus pneumoniae, Klebsiella pneumoniae, Pseudomonas aeruginosa. Listeria monocytogenes, and Vibrio cholerae were screened on a blood agar medium containing 0.1 mm PNPG, they displayed similar growth and hemolytic characteristics to the identical medium without PNPG.

Effects of p-fluorophenylalanine and chloramphenicol on chemotaxis in Escherichia coli.

The effects of chloramphenicol and p-fluorophenylalanine (p-FPA) on growth, proportion of motile cells, average rate of motility, and the chemotactic response of a methionine auxotroph of Escherichia coli K-12 were studied. Kinetic studies revealed that the inhibition of chemotaxis by p-FPA can be explained by the effect on growth, proportion of motile cells, and average rate of motility rather than a selective inhibition of chemotaxis per se. The effect of chloramphenicol on chemotaxis could not be explained in terms of these characteristics. It is concluded that low concentrations of chloramphenicol, unlike p-FPA, selectively inhibit chemotaxis.