The phylogenic position of Peptococcus niger based on 16S rRNA sequence studies

A 1330 base-pair fragment of a 16S rRNA gene has been amplified, cloned and sequenced. Comparison to other 16S rRNA sequences of eubacteria showed that P. niger represents a deep branch within the subdivision "Gram-positive with Gram-negative cell walls". It is not related to peptostreptococci, representatives of this genus studied so far are more closely related to clostridia.     

Formation and role of glycine betaine in the moderate halophile Vibrio costicola

The moderate halophile Vibrio costicola, growing on a chemically-defined medium, transformed choline into glycine betaine (betaine) by the membrane-bound enzyme choline dehydrogenase and the cytoplasmic enzyme betainal (betaine aldehyde) dehydrogenase. Choline dehydrogenase was strongly induced and betainal dehydrogenase less strongly induced by choline. The formation of these enzymes was also regulated by the NaCl concentration of the growth medium, increasing with increasing NaCl concentrations. Intracellular betaine concentrations also increased with increasing choline and NaCl concentrations in the medium. This increase was almost completely blocked by chloramphenicol, which does not block the increase in salt-tolerant active transport on transfer from a low to a high salt concentration.Choline dehydrogenase was inhibited by chloride salts of Na⁺, K⁺, and NH _inf4 ^su+ , the inhibition being due to the Cl^- ions. Betainal dehydrogenase was stimulated by 0.5 M salts and could function in up to 2.0 M salts.Cells grew as well in the presence as in the absence of choline in 0.5 M and 1.0 M NaCl, but formed no intracellular betaine. Choline stimulated growth in 2.0 M NaCl and was essential for growth in 3.0 M NaCl. Thus, while betaine is important for some of the adaptations to high salt concentration by V. costicola, it by no means accounts for all of them.Abbreviations CDMM chemically-defined minimal medium - PPT proteose-peptone tryptone medium - SDS sodium dodecyl sulfate Deceased, 1987     

Molecular basis for the special properties of proteins and enzymes from Halobacterium marismortui

Abstract Three proteins from Halobacterium marismortui , malate dehydrogenase (hMDH), glutamate dehydrogenase (hGDH) and ferredoxin (hFD) were purified and characterized with respect to their molecular masses, amino acid composition and, for hFD only, primary structure. Striking features of halophilic proteins are: the high excess of acidic over basic residues; acidic clusters in the sequence. Low-salt concentration causes inactivation and changes in structural parameters of hMDH and hGDH. Reactivation of hMDH involves long-lived stable intermediates. The salt concentration optimum of enzymic activity is independent of salt nature. The high capacity of halophilic proteins to retain water and salt is due to unique molecular properties, studied by physico-chemical techniques.     

Rhodospirillum salinarum sp. nov., a halophilic photosynthetic bacterium isolated from a Portuguese saltern

A new species of halophilic photosynthetic bacteria, Rhodospirillum salinarum, has been isolated and described. Its natural habitat are the terminal crystallization ponds of solar salt production plants. R. salinarum grows optimally at 42°C in the presence of 6–18% NaCl (w/v). Growth requirements are complex, yeast extract and peptone being required both for aerobic heterotrophic and for anaerobic phototrophic growth. Increasing concentrations of NaCl in the growth media did not give rise to any corresponding increase in intracellular concentrations of K⁺, Na⁺, polyalcohols or amino acids. Malate dehydrogenase from R. salinarum is not halophilic, being inhibited even at low concentrations of Na⁺ or K⁺. The GC mol % of DNA from R. salinarum is markedly higher than that for DNA from R. salexigens, the only previously described halophilic species of the genus Rhodospirillum.     

Ectothiorhodospira vacuolata sp. nov., a new phototrophic bacterium from soda lakes

A new phototrophic bacterium was isolated from Jordanian and Kenyan alkaline salt lakes. Cells are rod shaped, 1.5 m wide and 2–4 m long, and motile by polar flagella. They divide by binary fission, and possess photosynthetic membranes as lamellar stacks similar to those in the other species of the genus Ectothiorhodospira and the brown colored Rhodospirillum species. The presence of bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series is indicated by the absorption spectra of living cells. Under certain growth conditions the cells form gas vacuoles, may become immotile and float to the top of the culture medium. Sulfide and thiosulfate are used as photosynthetic electron donors. During the oxidation of sulfide to sulfate, elemental sulfur is formed, which is accumulated outside the cells. The organisms are strictly anaerobic, do not require vitamins, are moderately halophilic and need alkaline pH-values for growth. The new species Ectothiorhodospira vacuolata is proposed.     

Role of Central Metabolism in the Osmoadaptation of the Halophilic Bacterium Chromohalobacter salexigens

Bacterial osmoadaptation involves the cytoplasmic accumulation of compatible solutes to counteract extracellular osmolarity. The halophilic and highly halotolerant bacterium Chromohalobacter salexigens is able to grow up to 3 m NaCl in a minimal medium due to the de novo synthesis of ectoines. This is an osmoregulated pathway that burdens central metabolic routes by quantitatively drawing off TCA cycle intermediaries. Consequently, metabolism in C. salexigens has adapted to support this biosynthetic route. Metabolism of C. salexigens is more efficient at high salinity than at low salinity, as reflected by lower glucose consumption, lower metabolite overflow, and higher biomass yield. At low salinity, by-products (mainly gluconate, pyruvate, and acetate) accumulate extracellularly. Using [1-¹³C]-, [2-¹³C]-, [6-¹³C]-, and [U-¹³C₆]glucose as carbon sources, we were able to determine the main central metabolic pathways involved in ectoines biosynthesis from glucose. C. salexigens uses the Entner-Doudoroff pathway rather than the standard glycolytic pathway for glucose catabolism, and anaplerotic activity is high to replenish the TCA cycle with the intermediaries withdrawn for ectoines biosynthesis. Metabolic flux ratios at low and high salinity were similar, revealing a certain metabolic rigidity, probably due to its specialization to support high biosynthetic fluxes and partially explaining why metabolic yields are so highly affected by salinity. This work represents an important contribution to the elucidation of specific metabolic adaptations in compatible solute-accumulating halophilic bacteria.     

Microbiological and chemical quality of a traditional salted-fermented fish (Hout-Kasef) product of Jazan Region,Saudi Arabia

The Hout-Kasef is traditional salted fermented fish product of natural fermentation of salted mullet fish of coastal area of Jazan region of Saudi Arabia. The present study was carried out to investigate the microbiological and chemical characteristic of Hout-Kasef. A total of twenty-four salted fish samples were purchased from fish market in Jazan and Abu-Arish at different times of the year. The microbial studies of salted-fermented fish revealed a total bacterial count ranging from 2.81 to 4.72 Log₁₀ CFU/g, yeast and mold counts ranging from 0.48 to 3.14 Log₁₀ CFU/g, total staphylococci count 2.71–3.85 Log₁₀ CFU/g, halophile bacteria count 3.26–5.14 Log₁₀ CFU/g, and coliforms count <1 Log₁₀ CFU/g. However, pathogenic bacteria such as Listeria monocytogenes, Vibrio spp., Campylobacter spp. and Yersinia species were not detected. The major bacteria species isolated and identified from the salted fermented fish were Bacillus Subtilus, Bacillus mycoides, Bacillus licheniformis, Bacillus pumilus, Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus hominis, Staphylococcus xylosus, Staphylococcus saprophticus and Staphylococcus cahnii subsp cahnii. The chemical analysis of salted fermented fish showed high content of moisture (47.96%), protein (25.71%), ash (19.6%) and salt (15.19%) but low contents of lipid (7.25%). The salted-fermented fish also showed high level of total volatile basic nitrogen (78.86 mg/100 gm sample) and thiobarbutric acid number (32.32 mg malonaldehyde/kg) with a pH value of pH 6.3. Finally, this study showed the presence of gram positive and gram negative bacteria in the fish product. The predominant microorganisms found were Bacillus and Staphylococcus spp. The fish product had high content of salt and TVB-N levels.