Utilization of waste fish oil and glycerol as carbon sources for polyhydroxyalkanoate production by Salinivibrio sp. M318.

A moderately halophilic bacterium isolated from fermenting shrimp paste, Salinivibrio sp. M318 was found capable of using fish sauce and mixtures of waste fish oil and glycerol as nitrogen and carbon sources, respectively, for poly(3-hydroxybutyrate) (PHB) production. A cell dry weight (CDW) of up to 10 g/L and PHB content of 51.7 wt% were obtained after 48 h of cultivation in flask experiment. Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] was synthesized when 1,4-butanediol, γ-butyrolactone, or sodium 4-hydroxybutyrate was added as precursors to the culture medium. The biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] was achieved by supplying precursors such as sodium valerate, sodium propionate, and sodium heptanoate. Salinivibrio sp. M318 was able to accumulate the above mentioned PHAs during the growth phase. High CDW of 69.1 g/L and PHB content of 51.5 wt% were obtained by strain Salinivibrio sp. M318 after 78 h of cultivation in fed-batch culture. The results demonstrate Salinivibrio sp. M318 to be a promising wild-type bacterium for the production of PHA from aquaculture residues.

Public good dynamics drive evolution of iron acquisition strategies in natural bacterioplankton populations.

A common strategy among microbes living in iron-limited environments is the secretion of siderophores, which can bind poorly soluble iron and make it available to cells via active transport mechanisms. Such siderophore-iron complexes can be thought of as public goods that can be exploited by local communities and drive diversification, for example by the evolution of "cheating." However, it is unclear whether bacterial populations in the environment form stable enough communities such that social interactions significantly impact evolutionary dynamics. Here we show that public good games drive the evolution of iron acquisition strategies in wild populations of marine bacteria. We found that within nonclonal but ecologically cohesive genotypic clusters of closely related Vibrionaceae, only an intermediate percentage of genotypes are able to produce siderophores. Nonproducers within these clusters exhibited selective loss of siderophore biosynthetic pathways, whereas siderophore transport mechanisms were retained, suggesting that these nonproducers can act as cheaters that benefit from siderophore producers in their local environment. In support of this hypothesis, these nonproducers in iron-limited media suffer a significant decrease in growth, which can be alleviated by siderophores, presumably owing to the retention of transport mechanisms. Moreover, using ecological data of resource partitioning, we found that cheating coevolves with the ecological specialization toward association with larger particles in the water column, suggesting that these can harbor stable enough communities for dependencies among organisms to evolve.

Production of bioactive secondary metabolites by marine vibrionaceae.

Bacteria belonging to the Vibrionaceae family are widespread in the marine environment. Today, 128 species of vibrios are known. Several of them are infamous for their pathogenicity or symbiotic relationships. Despite their ability to interact with eukaryotes, the vibrios are greatly underexplored for their ability to produce bioactive secondary metabolites and studies have been limited to only a few species. Most of the compounds isolated from vibrios so far are non-ribosomal peptides or hybrids thereof, with examples of N-containing compounds produced independent of nonribosomal peptide synthetases (NRPS). Though covering a limited chemical space, vibrios produce compounds with attractive biological activities, including antibacterial, anticancer, and antivirulence activities. This review highlights some of the most interesting structures from this group of bacteria. Many compounds found in vibrios have also been isolated from other distantly related bacteria. This cosmopolitan occurrence of metabolites indicates a high incidence of horizontal gene transfer, which raises interesting questions concerning the ecological function of some of these molecules. This account underlines the pending potential for exploring new bacterial sources of bioactive compounds and the challenges related to their investigation.

Accumulation and role of compatible solutes in fast-growing Salinivibrio costicola subsp. yaniae.

The moderately halophilic bacterium Salinivibrio costicola subsp. yaniae showed an extremely fast growth rate. Optimal growth was observed in artificial seawater containing 1.4 mol/L NaCl and in MM63 media containing 0.6 mol/L NaCl. We analyzed a variety of compatible solutes that had accumulated in this strain grown in the media. The supplementation effect of the compatible solutes glycine betaine, glutamate, and ectoine to the growth of S. costicola subsp. yaniae was examined. Glycine betaine and glutamate had no supplementation effect on the fast growth rate. Growth of salt-sensitive mutants MU1 and MU2, both of which were defective in the ability to synthesize ectoine, was not observed in MM63 medium in the presence of more than 1.0 mol/L NaCl. From these data, we conclude that ectoine was the predominant compatible solute synthesized in this bacterium that effected an extremely fast growth rate.

Photobacterium rosenbergii sp. nov. and Enterovibrio coralii sp. nov., vibrios associated with coral bleaching.

Six new Vibrio-like isolates originating from different species of bleached and healthy corals around Magnetic Island (Australia) were investigated using a polyphasic approach. Phylogenetic analyses based on 16S rRNA, recA and rpoA gene sequences split the isolates in two new groups. Strains LMG 22223(T), LMG 22224, LMG 22225, LMG 22226 and LMG 22227 were phylogenetic neighbours of Photobacterium leiognathi LMG 4228(T) (95.6 % 16S rRNA gene sequence similarity), whereas strain LMG 22228(T) was related to Enterovibrio norvegicus LMG 19839(T) (95.5 % 16S rRNA gene sequence similarity). The two new groups can be distinguished from closely related species on the basis of several phenotypic features, including fermentation of d-mannitol, melibiose and sucrose, and utilization of different compounds as carbon sources, arginine dihydrolase activity, nitrate reduction, resistance to the vibriostatic agent O/129 and the presence of fatty acids 15 : 0 iso and 17 : 0 iso. The names Photobacterium rosenbergii sp. nov. (type strain LMG 22223(T)=CBMAI 622(T)=CC1(T)) and Enterovibrio coralii sp. nov. (type strain LMG 22228(T)=CBMAI 623(T)=CC17(T)) are proposed to accommodate these new isolates. The G+C contents of the DNA of the two type strains are respectively 47.6 and 48.2 mol%.

Enterovibrio norvegicus gen. nov., sp. nov., isolated from the gut of turbot (Scophthalmus maximus) larvae: a new member of the family Vibrionaceae.

Twenty-two isolates originating from the gut of healthy cultured turbot larvae in Norway were investigated using a polyphasic approach. Amplified fragment length polymorphism fingerprinting analysis showed that the isolates have typical patterns and form two main groups. Phylogenetic analysis revealed that the isolates belong to the gamma-Proteobacteria, with Vibrio hollisae as their closest neighbour. DNA-DNA hybridization, chemotaxonomic and phenotypic analyses further proved that these isolates represent a tight novel taxon that differs from currently described species in the family Vibrionaceae. It is proposed that these novel isolates be accommodated in a new genus, Enterovibrio gen. nov., with Enterovibrio norvegicus sp. nov. as the type species. Isolates were motile by a polar flagellum, positive for oxidase, catalase, arginine dihydrolase and beta-galactosidase, but negative for the Voges-Proskauer reaction. They produced indole, did not reduce nitrate and were resistant to the vibriostatic agent O/129. The DNA G+C content of E. norvegicus was 47.1-47.9 mol%. The type strain is E. norvegicus LMG 19839(T) (= CAIM 430(T)).

Iron uptake in Plesiomonas shigelloides: cloning of the genes for the heme-iron uptake system.

The iron uptake systems of Plesiomonas shigelloides strains were determined. Siderophore production was not detected by chemical or biological assays, and the strains tested were unable to use enterobactin, aerobactin, or vibriobactin for growth in low-iron media. Both hemin and hemoglobin supported full growth of the bacteria in media lacking other iron sources, but neither transferrin nor lactoferrin served as a source of iron. Hemolysin was detected, and the production of hemolysin was iron repressible. DNA sequences encoding hemolysin production and DNA sequences encoding the ability to use heme or hemoglobin as a sole source of iron were cloned from P. shigelloides and expressed in Escherichia coli. The abilities to use heme and hemoglobin as iron sources were closely linked, and the cloned sequences encoded the ability to transport the porphyrin, as well as iron, into the cells.

Cytotoxicity and suckling mouse reactivity of Aeromonas hydrophila isolated from human sources.

Human isolates of Aeromonas hydrophila and Plesiomonas shigelloides were tested for their ability to produce cytotoxins and (or) enterotoxins. The incidence of cytotoxin production by A. hydrophila was 81% for isolates from stool and 44% for extraintestinal isolates. Chinese hamster ovary (CHO) cells were more sensitive to A. hydrophila cytotoxin than either Vero or Y-1 mouse adrenal tumor cells (y-1). There was no evidence of cytotonic enterotoxin production by any of the isolates tested. Cytotoxin-containing filtrates from A. hydrophila were found to provoke a positive reaction in suckling mice. The response in mice was heat labile, and data supporting correlation of this activity with the cytotoxin produced by these organisms are presented. Following concentration, cytotoxin and material reactive in suckling mice were found to coelute from Sephadex G-25 and dose-response was demonstrated in mice. Antitoxin prepared to this material effectively neutralized cytotoxin, mouse reactivity, and rabbit ileal loop response. No evidence was obtained for either cytotoxin or enterotoxin production by P. shigelloides strains tested in this study.

AMP metabolism in the marine bacterium Beneckea natriegens.

The catabolism of AMP by preparations from Beneckea natriegens has been reexamined. In the absence of ATP, cell-free extracts catabolized AMP via adenosine to inosine. When ATP was present, adenylate kinase converted AMP to ADP, lowering the rate of AMP catabolism. Particle-free supernatants (225,000 x g) metabolized AMP alone slowly, but adenylate kinase was active when ATP was added. Washed particulate fractions contained AMP nucleotidase activity which converted AMP to adenosine; in the presence of ATP, adenosine formation was reduced by residual adenylate kinase associated with the particulate fraction. IMP was not detected as a metabolite in these experiments.

Fermentation of polysaccharides by Klebsielleae and other facultative bacilli.

Fermentations of 10 polysaccharides by species of the family Enterobacteriaceae were examined. Algin, guar, karaya, xanthan, and xylan were not fermented by any of the strains tested. Most of the activity was found in the tribe Klebsielleae. Klebsiella oxytoca fermented amylopectin (97% of the strains studied), carrageenan (100%), inulin (68%), polypectate (100%), and tragacanth (100%). Klebsiella pneumoniae fermented amylopectin (91%), carrageenan (100%), and tragacanth (86%). Carrageenan was also fermented by Enterobacter aerogenes (100%), Enterobacter agglomerans (63%), Enterobacter cloacae (95%), and Pectobacterium (38%). Pectobacterium shared polypectate fermentation (100%) with K. oxytoca. With one exception, Serratia strains were negative on all polysaccharides. These results, along with other evidence, indicate that (i) the genus Klebsiella is biochemically the most versatile genus of the tribe, (ii) because of its distinct characteristics, K. oxytoca warrants species designation separate from K. pneumoniae, and (iii) some food additives generally considered indigestible can be metabolized by a few species of facultative bacilli, whereas others appear to be resistant.

Differential synthesis of the polypeptides of aldehyde dehydrogenase and NAD(P)H:flavin oxidoreductase in the bioluminescent bacterium Beneckea harveyi.

The proteins of the bioluminescent bacterium Beneckea harveyi have been labelled with [3H]leucine prior to the induction of bioluminescence, and with [14C]leucine during the development of the bioluminescent system. An aliphatic aldehyde dehydrogenase and a NAD(P)H:flavin oxidoreductase, two enzymes that may be directly involved in the metabolism of the substrates (aldehyde, FMNH2) for the luminescent reaction catalyzed by luciferase, were purified and the isotope ratios of their respective polypeptide chains determined after sodium dodecyl sufate gel electrophoresis. A comparison of these isotope ratios to (a) the isotope ratios of the induced polypeptide chains of luciferase, purified in the same experiment, and (b) the average isotope ratio for the proteins synthesized in concert with growth has provided direct evidence that the synthesis of aldehyde dehydrogenase but not NAD(P)H:flavin oxidoreductase is induced during the development of bioluminescence.

Growth, luminescence, respiration, and the ATP pool during autoinduction in Beneckea harveyi.

The bacterial bioluminescence system is unusual because it is self-induced. In the late logarithmic phase of growth, upon the accumulation of an autoinducer, the synthesis of the components of the system is initiated. We were interested in determining what effect this burst of synthesis and activity has on cellular energy metabolism. The ATP pool of the luminous bacterium Beneckea harveyi was found to dip 10- to 20-fold during the luminescence period, while the respiration per unit cell mass (optical density) increased but by much less. The dip in the ATP pool did not occur in four different types of dark mutants, including one that was temperature conditional and another that was conditional upon added cyclic AMP for luminescence. However, it is neither the synthesis nor the activity of luciferase that is responsible for the ATP dip; the dip does not occur in certain dark "aldehyde" mutants which nevertheless synthesize normal levels of luciferase, whereas it does occur at 36 degrees C in a temperature-sensitive luciferase mutant which forms normal levels of inactive luciferase. Results with other aldehyde mutants implicate the pathway involved in the synthesis of the aldehyde factor with the ATP dip.

Adenylate energy charge during batch culture of Beneckea natriegens.

The value of the adenylate energy charge, i.e. ([ATP] + 1/2[ADP])/([ATP] + [ADP] + [AMP]), during batch culture of Beneckea natriegens remained relatively constant during the exponential and early stationary phases of the growth cycle. During exponential growth the intracellular ATP content remained constant, the amount of ATP in the culture increasing proportionally with growth; these conditions were unaltered during growth in the presence of added cyclic AMP. On cessation of growth, significant variation in bacterial ATP content was observed depending on whether growth of the cultures terminated due to exhaustion of carbon or nitrogen from the medium, and on the presence or absence of added cyclic AMP.