Microbial assessment and quality evaluation of ogi during spoilage

The changes during the fermentation of ogi, a cereal-based traditional lactic acid-fermented weaning food were studied up to the spoilage stage. Ogi off-odour was first noticed at the fourth day of fermentation (including 24 h steeping). Yeast isolates such as Candida valida, C. krusei, Geotrichum candidum and bacteria like Lactobacillus brevis, L. plantarum, Pediococcus pentosaceus, Bacillus subtilis, Brevibacterium linens, Br. oxydans and other two Brevibacterium spp. dominated the fermenting mash at the spoilage stage. The brevibacteria contributed most significantly to ogi off-odour. Ogi samples inoculated with lactic acid bacteria increased acidity and product acceptability over the time of fermentation. The pH, titratable acidity, dissolved hydrogen sulphide and the presence of brevibacteria appear as good indices for monitoring spoilage. Hydrogen sulphide (H₂S) levels appear to be the most useful of the parameters studied. No coliforms and clostridia were identified during spoilage.     

Inhibition and Agglutination of Arthrobacters by Pseudomonads

The bacterial flora of water in Narragansett Bay, R.I., was observed semimonthly from 1962 to 1964. Dominant isolates were keyed to genus, and the isolates for each genus were expressed as percentage of total isolates. There was a consistent inverse relationship between arthrobacters and the dominant pseudomonads. Pseudomonad growth on agar plates markedly inhibited arthrobacter cross-streaks. Agar from inhibition zones as well as supernatant fluids from pseudomonad broth cultures inhibited arthrobacter motility and caused the cells to agglutinate. Gummy pseudomonad residues from vacuum-evaporated broth cultures readily passed a G-25 Sephadex column. This material agglutinated arthrobacter cells, but failed to cause arthrobacter inhibition in filter-pad assays. In contrast, sterile medium inside a dialysis sac, inoculated externally with a pseudomonad, was inhibitory to arthrobacters in pad assay but failed to agglutinate arthrobacter cells. Pseudomonad isolates from soil showed similar inhibiting and agglutinating activities for both soil and seawater arthrobacter isolates. The inhibitory and agglutinating activities of pseudomonad isolates appeared to diminish on prolonged laboratory cultivation.     

Discovery and distribution of super-integrons among Pseudomonads

Until recently, integrons (systems for acquisition and expression of new genetic materials) have been associated generally with antibiotic resistance gene cassettes. The discovery of 'super-integrons' in Vibrionaceae suggests a greater impact of this gene acquisition mechanism on bacterial genome evolution than initially believed. Super-integrons may contain more than 100 gene cassettes and may encode other determinants, including biochemical functions or virulence factors. Here, we report the genetic organization of a super-integron from Pseudomonas alcaligenes ATCC 55044. This is the first evidence of a super-integron in a non-pathogenic bacterium, one which is widely distributed in a great number of ecological niches such as soil and aquatic habitats. Here, the sequence composition, open reading frame (ORF) content and organization of In55044 are described and found to have features intermediate between the multidrug-resistant integrons and the Vibrio cholerae super-integron. Similar structures are inferred to be present in several Pseudomonas species, based on polymerase chain reaction (PCR) experiments.     

New Medium for the Isolation and Enumeration of Pseudomonads

A new medium containing 200 ppb of 2-hydroxy-2',4,4'-trichlorodiphenyloxide (CH3565) and 10 ppm of cetyl-trimethyl-ammonium bromide (Cetrimide) in tryptic soy agar was developed and tested with 19 pure cultures of Pseudomonas, 20 microorganisms of other genera, commercially prepared ground beef, and laboratory-prepared inoculated ground beef. The new medium, CETCH agar, was compared with an antibiotic-containing medium. CETCH agar provided greater pseudomonad recoveries, a shorter incubation period prior to plate counting, and greater ease of preparation.     

An improved method of transformation in Pseudomonads

Summary A protocol for producing competent Pseuclomonas aeruginosa, Pseudomonas putida, and Xanthomonas maltophilia was adapted and modified from existing methods. Cells were incubated on ice for 30 minutes in buffered 100 mM MgCl₂ followed by 30 minutes in buffered 100 mM CaCl₂ prior to addition of DNA. The MgCl₂-CaCl₂ incubation increased transformation efficiency two to three times, compared with protocols which use incubation in either Mg²⁺ or Ca²⁺, but not both.     

The mechanisms of nitrogen assimilation in Pseudomonads

Pseudomonas aeruginosa, Ps. fluorescens and 3 marine psychrophylic pseudomonads were grown in chemostat cultures with nitrate ammonia or glutamate as nitrogen source. In cultures grown on nitrate (either carbon- or nitrogen-limited) and in ammonia nitrogen-limited cultures ammonia was assimilated via the GS/GOGAT pathway. With a excess of ammonia in the culture however ammonia was assimilated via GDH and GS was either present only at low levels or absent. Two distinct GDH activities were detected in all 5 bacteria, one specific to NAD and one to NADP. The presence of these activities was determined by the environment in which cells were grown. These activities showed differences with respect to substrate affinity (Km values) for ammonia, incubation temperature and to a lesser extent pH and may involve separate GDH isoenzymes. GS from the marine bacterium PL₁ had a very high affinity for ammonia (Km of 0.3mm) but a low affinity for glutamate (Km of 19mm).     

Cross-Species GacA-Controlled Induction of Antibiosis in Pseudomonads

Signal extracts prepared from culture supernatants of Pseudomonas fluorescens CHA0 and Pseudomonas aeruginosa PAO stimulated GacA-dependent expression of small RNAs and hence of antibiotic compounds in both hosts. Pseudomonas corrugata LMG2172 and P. fluorescens SBW25 also produced signal molecules stimulating GacA-controlled antibiotic synthesis in strain CHA0, illustrating a novel, N-acyl-homoserine lactone-independent type of interspecies communication.     

Enrichment and Isolation of Naphthalenesulfonic Acid-Utilizing Pseudomonads

Naphthalenesulfonate-degrading bacteria were obtained by continuous enrichment from a naphthalene-degrading population from sewage. In addition to naphthalene, Pseudomonas sp. A3 can utilize 2-naphthalenesulfonate (2NS) and Pseudomonas sp. C22 can utilize both 1-naphthalenesulfonate (1NS) and 2NS as sole carbon sources. In a mixture of 1NS and 2NS, the former substrate is utilized by strain C22 only after complete consumption of 2NS. During exponential growth, approximately 10% of the organic carbon of naphthalenesulfonates is temporarily excreted. These unidentified metabolites can readily be used by other bacteria, which, by supplying strain C22 with vitamins, allow optimal growth in stable mixed cultures. The degradative capability of Pseudomonas sp. A3 for 2NS was irreversibly lost under nonselective growth conditions and could be transferred from the wild type to a distinguishable cured strain of the wild type.     

Evolutionary Insight into the Functional Amyloids of the Pseudomonads

Functional bacterial amyloids (FuBA) are important components in many environmental biofilms where they provide structural integrity to the biofilm, mediate bacterial aggregation and may function as virulence factor by binding specifically to host cell molecules. A novel FuBA system, the Fap system, was previously characterized in the genus Pseudomonas, however, very little is known about the phylogenetic diversity of bacteria with the genetic capacity to apply this system. Studies of genomes and public metagenomes from a diverse range of habitats showed that the Fap system is restricted to only three classes in the phylum Proteobacteria, the Beta-, Gamma- and Deltaproteobacteria. The structural organization of the fap genes into a single fapABCDEF operon is well conserved with minor variations such as a frequent deletion of fapA. A high degree of variation was seen within the primary structure of the major Fap fibril monomers, FapC, whereas the minor monomers, FapB, showed less sequence variation. Comparison of phylogenetic trees based on Fap proteins and the 16S rRNA gene of the corresponding bacteria showed remarkably similar overall topology. This indicates, that horizontal gene transfer is an infrequent event in the evolution of the Fap system.     

Fine Structure of Selected Marine Pseudomonads and Achromobacters

The fine structure of more than 20 marine pseudomonads and more than 15 achromobacters was examined. Under the conditions extant, clear differences between members of these two groups were seen. The pseudomonads displayed the characteristic gram-negative morphology: the cell wall was irregularly undulant and the cytoplasmic membrane more nearly planar, ribonucleoprotein (RNP) particles were loosely packed throughout the periphery of the cytoplasm, and the deoxyribonucleic acid (DNA) was axially disposed. Cell division appeared to be by constriction. Some strains characteristically produced evaginations or blebs of the cell wall. Occasionally, thick, densely stained ring structures were seen which are possibly analogous to mesosomes. In contrast, the achromobacters demonstrated a regularly undulant outer cell wall element and a planar inner wall. The cytoplasmic membrane was thin and not readily observed. RNP particles were densely stained and tightly packed in the cytoplasm; the DNA was most often lobate in disposition. Cellular division was mediated by the formation of a septum which consisted of the cytoplasmic membrane and the inner element of the cell wall. Mesosomes were observed in all of the strains examined. Dense inclusion bodies were also seen in many strains.     

Linking prey composition of haddock Melanogrammus aeglefinus to benthic prey availability in three different areas of the northern North Sea

The feeding strategy and prey selection of haddock Melanogrammus aeglefinus related to the benthic infauna in the field were investigated in three different study areas (boxes) in the northern North Sea in 2007. The stomach contents of M. aeglefinus were dominated by invertebrates in all three boxes, mainly echinoderms and polychaetes, similar to the benthic communities in the field. Prey densities in the field significantly determined prey selection and, thus the feeding strategy of M. aeglefinus appeared highly opportunistic. Other prey characteristics, such as the position in the sediment or its palatability, had no significant effect on the selection process although trends were apparent that tubicolous polychaetes of the family spionids, especially Spiophanes kröyeri and Spiophanes bombyx as well as the tentaculate Phoronis spp., were not consumed and potentially avoided due to their ability to withdraw below the feeding depths or due to chemical deterrents. High abundances of echinoderm species with hard calcareous shells in the M. aeglefinus stomachs, such as the ophiurid Ophiocten affinis and the echinoid Echinocyamus pusillus, indicated their use as grinding elements. A gradual shift from benthos to fish feeding with increasing M. aeglefinus size was not found.     

Detection of irradiated spices by different physical techniques

We used thermoluminescence, electron spin resonance, and viscosimetric measurements to establish whether or not a spice had been irradiated. Thermoluminescence, using the 1788 EN official protocol with an alternative method for the extraction of mineral impurities, led to proof of irradiation or proof of no treatment. Electron spin resonance led to different spectrum shapes depending on the chemical composition of the spices; ESR could only be used as proof of irradiation up to several weeks after irradiation, and only for some spices. Viscosimetric measurements carried out on spice suspensions led to a presumption of treatment (or of no treatment) and possibly to proof of irradiation.