Screening ofBifidobacterium strains for bacteriocin production

Summary Thirteen strains of bifidobacteria (Bifidobacterium) were examined for bacteriocin production. One strain among these produced bacteriocin which is active against lactic streptococci strains and against other species ofBifidobacterium, Clostridium andLactobacillus, but not against Gram-negative bacteria such asPseudomonas, Klebsiella, Serratia andEscherichia coli.Bacteriocin activity was inhibited by proteolytic enzymes, but not by heating 15 min or30 min at 100°C, and it was resistant for 15 min at 121°C and active at pH between 2 to 10.     

Photodynamic effects of deuteroporphyrin on Gram-positive bacteria

The photodynamic effects of deuteroporphyrin (DT) on the growth and viability ofStaphylococcus aureus, Streptococcus faecalis, andBacillus cereus are described. By exposure to light and DT, the growth ofSta. aureus andStr. Faecalis strains was markedly inhibited, whereasB. cereus was undergoing lysis. Counting the viable bacteria during the DT treatment revealed that more than 99% of the initial bacterial population was killed within the first 30 min of treatment. The pH dependence of the photodynamic inhibitory effect shows that it is best obtained at pH 6.5. No temperature dependence in the range of 37°–44°C could be detected. The best photodynamic effect was achieved when the culture was in the mid-log phase. DT-treated bacteria, when grown in the dark or in the presence of horse serum albumin, were unaffected by the porphyrin action. Electron microscopic examinations ofSta. aureus andStr. faecalis showed the appearance of well-developed mesosomes within the cell cytoplasm.B. cereus preparations have not shown any mesosome formation but showed some lysed cells as well as some spores. None of the mentioned effects by DT and light could be observed on Gramnegative bacteria such asEscherchia coli orPseudomonas aeruginosa.     

Characterization and identification of bacteria isolated from micropropagated mint plants

Summary Bacterial isolates from contaminated mint shoot cultures were characterized and identified as a preliminary step in determining an elimination treatment. The 22 bacteria were characterized using biochemical and morphological tests and subjected to sensitivity tests with four antibiotics. The isolates were compared with known organisms and assigned to genera according to similarities in characteristics. Seven isolates were analyzed by fatty acid analysis carried out by a commercial laboratory. Six were classified asAgrobacterium radiobacter; eight asXanthomonas; one each asPseudomonas fluorescens, Micrococcus spp.,Corynebacterium spp., andCurtobacterium spp.; four could not be assigned to genera. Inhibition of growth of the bacteria by most antibiotics was best at pH 7.5. Minimal inhibitory concentration and minimal bactericidal concentrations of gentamicin, rifampicin, streptomycin sulfate, and Timentin varied with genotype.     

Biosurfactant production by two isolates ofPseudomonas aeruginosa

Two strains of biosurfactant-producing bacteria, identified asPseudomonas aeruginosa, were isolated from injection water and crude oil-associated water in Venezuelan oil fields. Both biosurfactants resembled rhamnolipids and produced stable emulsions of heavy and extra-heavy crude oils, reducing the surface tension of water from 72 to 28 dynes/cm. Tenso-active properties of the biosurfactants were not affected by pH, temperature, salinity or Ca²⁺ or Mg²⁺ at concentrations in excess of those found in many oil reservoirs in Venezuela.     

Application of microelectrode technique to measure pH and oxidoreduction potential gradients in gelled systems as model food

A microelectrode system is used in order to simultaneously measure pH and oxidoreduction potential (Eh) gradients developed during growth by Escherichia coli and Lactobacillus plantarum immobilized in gelled media used as model food. Unlike E. coli, L. plantarum steadily decreased medium pH independently of depth of measurement and time of incubation. Both bacteria brought about the creation of an Eh gradient throughout the gelled medium. This gradient was much more important for E. coli (700 mV) than for L. plantarum (80 mV) but more transitory.     

Isolation and partial characterization of bacteriocins from<Emphasis Type="Italic"> Pediococcus</Emphasis> species

Lactic acid bacteria have received increased attention as a potential food preservative due to their strong antagonistic activity against many food-spoilage and pathogenic organisms. Three Pediococcus species, P. acidilactici NCIM 2292, P. pentosaceous. NCIM 2296 and P. cervisiae NCIM 2171, were evaluated for bacteriocin production. Inhibitory substance were produced during the late growth phase and maximum production occurred at 37 °C after 36–48 h of incubation. Bacteriocins partially purified from these species by cold-acetone precipitation at 0 °C and cell adsorption desorption techniques have a broad inhibitory spectrum against microorganisms, including gram-negative bacteria such as Escherichia coli and Pseudomonas. Proteolytic enzymes inactivated these peptides, but amylase and lipase did not show any effect. The bacteriocins were stable over a wide pH range (3–8) and apparently most active at pH 4.0–5.0. They were heat-stable (1 h at ~80 °C and autoclaving) at pH 5.0. No loss in activity was observed when stored under refrigeration (4–8 °C). Tris-Tricine SDS-PAGE revealed the molecular masses of these peptides to be between 3.5 and 5.0 kDa.     

Biotransformation of anisole and phenetole by aerobic hydrocarbonoxidizing bacteria

Wild type, mutant, and recombinant bacterial strains capable of oxidizing aromatic hydrocarbons were screened for their ability to oxidize anisole (methoxybenzene) and phenetole (ethoxybenzene). Toluene-induced cells ofPseudomonas putida F39/D transformed anisole to a compound tentatively identified ascis-1,2-dihydroxy-3-methoxyclohexa-3,5-diene (anisole-2,3-dihydrodiol), 2-methoxyphenol, catechol, and trace amounts of phenol while phenetole was converted primarily tocis-1,2-dihydroxy-3-ethoxycyclohexa-3,5-diene (phenetole-2,3-dihydrodiol) and 2-ethoxyphenol. Induced cells ofPseudomonas sp. NCIB 9816/11 andBeijerinckia sp. B8/36 transformed anisole to phenol, and phenetole to phenol and ethenyloxybenzene. Toluene-induced cells ofP. putida BG1 converted anisole to phenol but did not oxidize phenetole. In contrast, toluene-induced cells ofP. mendocina KR1, which oxidize toluene via monooxygenation at thepara position, transformed anisole to 4-methoxyphenol, and phenetole to 2-, 3- and 4-ethoxyphenol. The involvement of toluene and naphthalene dioxygenases in the reactions catalyzed by strains F39/D and NCIB 9816/11, respectively, was confirmed with recombinantE. coli strains expressing the cloned dioxygenase genes. The results show that the oxygenases from differentPseudomonas strains oxidize anisole and phenetole to different hydroxylated products.     

Effect of chemical fertilizers on the transport ofEscherichia coli,Pseudomonas aeruginosa andSalmonella infantis through sand columns

Five commercial fertilizers, Amfos, ammonium sulfate, Kamex, Kieserit and NPK affected the transport ofEscherichia coli, Pseudomonas aeruginosa andSalmonella infantis in sand columns. The percentage of cells transported through sand without fertilizers during a 2-h period was species-dependent (0.56 forS. infantis, 3.1 forE. coli and 12.4 forP. aeruginosa). The cell transport was enhanced by Kamex for all strains tested, whereas Amfos was found to decrease the transport ofE. coli andS. infantis cells. A mathematical model revealed a relationship between the transport of cells and the pH of the sand columns with fertilizers. Columns in which the pH was decreased by the fertilizers exhibited a higher retention of cells. This points to the existence of physico-chemical surface interactions between cells and sand particles.     

Hydration of Oleic Acid by Enterococcus gallinarum, Pediococcus acidilactici andLactobacillus sp. Isolated from the Rumen

Three ruminal bacteria found to convert oleic acid to 10-hydroxystearic acid were identified asEnterococcus gallinarum , Pediococcus acidilactici and a lactobacillus physiologically similar toLactobacillus reuteri and L. fermentum. The oleic acid-hydrating properties of the three bacteria were determined and hydration was shown to be predominantly a feature of anaerobic culture with relatively little hydration occurring in aerobic culture. Hydration was highly pH dependent and not related to cell growth. At the optimal hydration pH for each bacterium, hydration yields were 97%, 93% and 76% for the E. gallinarum, P. acidilactici andLactobacillus strains, respectively. The enterococcus and the lactobacillus hydrated oleic acid only after growth ceased whereas the pediococcus hydrated oleic acid during the late logarithmic growth. Hydration was not specific for oleic acid with all three bacteria hydrating the oleic acid homologue palmitoleic acid. None of the bacteria hydrogenated oleic acid to stearic acid. Our results suggest that a capacity to hydrate oleic acid may be a property of many lactic acid bacteria.     

Dinitrogen fixation and infection of grass leaves byPseudomonas rubrisubalbicans andHerbaspirillum seropedicae

Bacteria causing mottled stripe disease in sugar cane, known asPseudomonas rubrisubalbicans, were shown to be able to fix molecular N₂ and to grow on it. The root associated diazotroph known asHerbaspirillum seropedicae, after artificial inoculation caused mottled stripe disease symptoms on sorghum and Napier grass but not on sugar cane. Both bacteria could be reisolated from leaves even 60 days after. Sugar cane leaves contained large numbers of these bacteria even in the uninoculated controls. Additional physiological characteristics of six strains ofP. rubrisubalbicans were compared with those of twoH. seropedicae strains and were shown to be very similar.     

Coliforms and enterococci isolated from the intestinal tract of conventional mice

Coliforms and enterococci were isolated from the intestinal tract of infant (12-day-old) and adult (6-to 8-week-old) conventional mice. Eighty coliform isolates and eighty enterococcal strains were grouped according to their ability to ferment or hydrolyze various substrates. Sixty-one of the coliform isolates were identified asEscherichia coli. The remaining 19 strains were similar toE. coli, but did not produce-galactosidase. The enterococci belonged to two species:Streptococcus faecium andS. faecalis. Four biotypes ofS. faecium and two biotypes ofS. faecalis were detected. Xylosefermenting enterococci were isolated with a higher frequency from infant mice than from adults.     

Isolation and characterization of acetonitrile utilizing bacteria

Summary Bacteria utilizing high concentrations of acetonitrile as the sole carbon source were isolated and identified asChromobacterium sp. andPseudomonas aeruginosa. Maximum growth was attained after 96 h of incubation andP. aeruginosa grew slightly faster thanChromobacterium sp. The strains were able to grow and oxidize acetonitrile at concentrations as high as 600 mM. However, higher concentrations inhibited growth and oxygen uptake. Degradation studies with (¹⁴C)acetonitrile indicated 57% of acetonitrile was degraded byPseudomonas aeruginosa as compared to 43% byChromobacterium. The isolates utilized different nitrile compounds as carbon substrates.     

Antifungal compounds produced by bacterial populations of the Sea SpongeVerongia sp.

The taxonomic structure and some metabolic features of the bacterial populations of the sea spongeVerongia sp were studied. Twenty-three symbiotrophic strains were isolated into axenic cultures and identified. These wereProteobacteria of the generaPseudoalteromonas andVibrio (about 52%), firmicutes with low G+C content (up to 22%), and bacteria of the generaFlavobacterium/Cytophaga/Bacteroides (13% of the strains studied). The strain KMM 3427, identified asBacillus subtilis, synthesized the secondary metabolite 2-p-hydroxyphenylalcohol (tyrosol), which is known to be an antifungal compound and may perform the function of chemical defence inVerongia sp.     

Antimicrobial activities of 2-arylthio-N-alkylmaleimides

Summary A variety of 2-arylthio-N-alkylmaleimides were prepared, and their antimicrobial activities were examined. Almost all of these compounds exhibited antibacterial activity against Gram-positive bacteria such asBacillus subtilis andStaphylococcus aureus. Some compounds such as 2-(halogeno-phenyl)-thio-N-methylmaleimides (4, 5, 6, 8 and 10) and 2-(2-carbamoylphenyl)thio-N-methylmaleimide(35) exhibited antibacterial activity againstEscherichia coli. All compounds tested were inactive againstPseudomonas aeruginosa except 2-(2-carbamoylphenyl)thio-N-methylmaleimide(35) which was marginally active. Activities against Gram-positive bacteria were not due to the effect of the substituent on the benzene ring, except in the instances 2-carboxy, 2-carbomethoxy, 2-amino groups and alkyl chains, however, activities against Gram-negative bacteria were due to phenylthio and the alkyl substituents. Some of 2-arylthio-N-alkylmaleimides were examined for their antifungal activities using eight strains of fungi, and they showed activity against these.     

Thermophilic amylase-producing bacteria from Vietnamese soils

Of 25 bacterial isolates from Vietnamese soils, two were identified asBacillus stearothermophilus and one asThermoactinomyces thalpophilus, both thermophilic, amylase-producing bacteria. Amylase activity was highest in the presence of cassava starch as carbon source and (NH₄)₂HPO₄ as nitrogen source. The strains exhibit a high amylase productivity within the first 5 to 7 h of cultivation at 55°C. The crude enzyme had optima of pH 6.5 and 70°C.     

Monoclonal antibodies againstAgrobacterium tumefaciens strain C58

Hybridoma cell lines were derived from the fusion of mouse myeloma cells with spleen cells from a mouse that had been immunized withAgrobacterium tumefaciens strain A759, a flagella-less mutant of strain C58 containing the Ti plasmid of strain B6. All of the 20 antibodies produced by the cloned hybridomas reacted with strain C58 and with other strains derived from C58. The antibodies did not react with 34 other strains ofA. tumefaciens, representing the three biovars, or with strains ofA. radiobacter, A. rubi, Rhizobium leguminosarum, R. meliloti, or other plant-associated bacteria such asErwinia herbicola andPseudomonas syringae. In addition to reacting with whole cells of strain A759, the antibodies reacted with phenol-water extracts of A759, indicating that they may recognize the lipopolysaccharide. These antibodies may be useful for ecological and epidemiological studies ofA. tumefaciens strain C58 in the agroecosystem.     

Fate of genetically modified microorganisms in the corn rhizosphere

The fates of genetically modified (GM)Escherichia coli andPseudomonas putida in the corn rhizosphere were investigated. Under hydrophonic and sterile conditions, both bacteria grew well in the presence of root exudates used as a sole carbon source. The growth patterns of wild types and genetically modified strains ofE. coli andP. putida were similar under the conditions tested.The presence of rhizospheric microorganisms affected the survival pattern ofE. coli. In the presence of corn roots and rhizospheric microorganisms,E. coli numbers increased during the first 3 days but were later drastically reduced, probably as a result of competition with rhizospheric microorganisms for the carbon source. However, in the presence of rhizospheric microorganisms,P. putida survived better thanE. coli in the simulated corn rhizosphere.     

Evidence for a plasmid conferring salt-tolerance in the plant-root associated,diazotrophKlebsiella sp. NIAB-I

Summary Using analytical and preparative methods, we demonstrated the presence of an indigenous plasmid (pNIAB-I) in a diazotroph,Klebsiella sp. NIAB-I isolated, from the roots of Kallar grass, growing on saline lands in Pakistan. The plasmid is approximately 50 kilobase (kb) in size. Transformation experiments indicated that non-halophilic bacteria such asE. coli K12 strain (MV10) andK. pneumoniae M5AI on acquiring this plasmid become tolerant to high salt (NaCl) and alkaline pH.     

Microbiological characterization of a fuel-oil contaminated site including numerical identification of heterotrophic water and soil bacteria

Seven soil samples and seven groundwater samples from a site contaminated with fuel-oil were investigated using several chemical and microbiological techniques. In soil samples, 500 to 7,500 mg/kg of total hydrocarbons were found. These samples contained no n-alkanes but iso- and branched chain alkanes. No polychlorinated biphenyls could be detected. Microbiological investigations included estimations of total cell counts, viable cell counts on different media, and numbers of methylotrophic, denitrifying, sulphate reducing, anaerobic (with the exception of methanogenic organisms), and hydrocarbon degrading bacteria. Viable and hydrocarbon degrading bacteria were found in all samples. A total of 1,366 pure cultures was characterized morphologically and physiologically and identified by numerical identification using a data base of more than 4,000 reference strains. Groundwater samples were dominated by gram-negative bacteria of the generaPseudomonas, Comamonas, Alcaligenes, andAcinetobacter, which were also found in soil samples. In addition, more grampositive bacteria belonging to the generaArthrobacter, Nocardia, andBacillus could be isolated from soil samples.     

Marine sponges as habitats of anaerobic phototrophic bacteria

Enrichment cultures were prepared with different media for phototrophic bacteria from four species of marine sponges, collected from oxic coastal waters near Split (Yugoslavia). We obtained pure cultures of six strains ofChromatiaceae and two strains ofRhodospirillaceae by agar shake dilution. TheRhodospirillaceae were identified asRhodopseudomonas sulfidophila and a marine form ofRhodopseudomonas palustris. TheChromatiaceae were identified asChromatium vinosum, Chromatium gracile, Chromatium minutissimum. Ectothiorhodospira mobilis, and a Chromatium species, which in some respects resemblesChromatium minus. The occurrence of strictly anaerobic phototrophic bacteria in aerobic sponges is discussed with respect to nutrition and possible syntrophism.