A detailed phenotypic characterisation of the type strains of Halomonas species

We have made a detailed phenotypic characterisation of the type strains of 21 species within the genus Halomonas and have also studied any possible intraspecific variation of strains within H. eurihalina, H. halophila, H. maura and H. salina. We used 234 morphological, physiological, biochemical, nutritional and antimicrobial susceptibility tests. Nutritional assays were carried out using both classical and miniaturized (BIOLOG system) identification methods. Two different numerical analyses were made using the TAXAN program; the first included the differential data from all the tests carried out whilst the second used only the 57 tests with the highest diagnostic scores (> or = 0.5). The results of both analyses were quite similar and demonstrated the phenotypic heterogeneity of the Halomonas species in question. At a 62% similarity level the type species were grouped into three phena, the main difference between them being the capacity of those included within phenon A (H. aquamarina, H. meridiana, H. cupida, H. pantelleriensis and H. halmophila) to produce acids from sugars. The species grouped in phenon C (H. campisalis, H. desiderata and H. subglasciescola) used fewer organic substrates than the others. The remaining strains were included in phenon B. H. marisflavi was clearly distinct and thus was not included in any of the three phena. High phenotypic similarity (more than 88%) was found between Halomonas campisalis and Halomonas desiderata. The results of our work should allow researchers to minimise the tests required to arrive at a reliable phenotypic characterisation of Halomonas isolates and to select those of most use to differentiate Halomonas species from each other.

Unsterile and continuous production of polyhydroxybutyrate by Halomonas TD01

An unsterile and continuous fermentation process was developed based on a halophilic bacterium termed Halomonas TD01 isolated from a salt lake in Xinjiang, China. The strain reached 80 g/L cell dry weight containing 80% poly(3-hydroxybutyrate) (PHB) on glucose salt medium during a 56 h fed-batch process. In a 14-day open unsterile and continuous process, the cells grew to an average of 40 g/L cell dry weight containing 60% PHB in the first fermentor with glucose salt medium. Continuous pumping of cultures from the first fermentor to the second fermentor containing the nitrogen-deficient glucose salt medium diluted the cells but allowed them to maintain a PHB level of between 65% and 70% of cell dry weight. Glucose to PHB conversions were between 20% and 30% in the first fermentor and above 50% in the second one. This unsterile and continuous fermentation process opens a new area for reducing the cost in polyhydroxyalkanoates production.

Halomonas organivorans sp. nov., a moderate halophile able to degrade aromatic compounds

A group of moderately halophilic bacteria able to degrade aromatic organic compounds contaminating hypersaline habitats in southern Spain have been isolated and characterized. The taxonomic position of these strains was determined using phenotypic, phylogenetic and genotypic methods. The G+C content of their DNA ranged from 61·0 to 62·9 mol%. DNA–DNA hybridization studies showed that they constitute a genospecies, having DNA–DNA hybridization values of 90–100 %. Analysis of the complete 16S rRNA gene sequence revealed a high level of similarity with members of the genus Halomonas, sharing 98 % 16S rRNA gene sequence similarity with the type strains of Halomonas salina and Halomonas halophila. However, phenotypic differences and the low level of DNA–DNA hybridization suggest the placement of these strains as a novel species within the genus Halomonas. The name Halomonas organivorans sp. nov. is proposed, with strain G-16.1T (=CECT 5995T=CCM 7142T) as the type strain. This novel species of Halomonas is characterized by its ability to use a wide range of organic compounds (benzoic acid, p-hydroxybenzoic acid, cinnamic acid, salicylic acid, phenylacetic acid, phenylpropionic acid, phenol, p-coumaric acid, ferulic acid and p-aminosalicylic acid), and it could be useful for the decontamination of polluted saline habitats.

Halomonas alimentaria sp. nov., isolated from jeotgal, a traditional Korean fermented seafood

A gram-negative, moderately halophilic bacterial strain, YKJ-16T, which was isolated from jeotgal, a traditional Korean food, was considered to be a member of the genus Halomonas. Cells of strain YKJ-16T are non-motile and cocci or short rods, unlike most Halomonas species. However, chemotaxonomic and phylogenetic analyses demonstrated that strain YKJ-16T belongs to the genus Halomonas. The predominant isoprenoid quinone is ubiquinone-9. The major fatty acids are C18.1omega7c, C16:0, C19:0 cyclo omega8c and C16:1omega7c and/or iso C15:0 20H. The phylogenetic tree showed that strain YKJ-16T forms a distinct evolutionary lineage within the radiation comprising Halomonas species and forms a coherent cluster with Halomonas halodenitrificans, Halomonas cupida and Halomonas pacifica. Levels of 16S rDNA similarity between strain YKJ-16T and the type strains of other Halomonas species are 93.0-96.3%. Levels of DNA-DNA relatedness indicate a taxonomic status of strain YKJ-16T as a species different from the three species that form the coherent cluster mentioned above. Morphologically, strain YKJ-16T is also clearly differentiated from the type strains of H. cupida and H. pacifica. Accordingly, on the basis of the phenotypic characteristics, 16S rDNA sequence analysis and DNA relatedness data, strain YKJ-16T should be placed in the genus Halomonas as a novel species. The name Halomonas alimentaria sp. nov. is proposed with strain YKJ-16T (= KCCM 41042T = JCM 10888T) as the type strain.

Halomonas neptunia sp. nov., Halomonas sulfidaeris sp. nov., Halomonas axialensis sp. nov. and Halomonas hydrothermalis sp. nov.: halophilic bacteria isolated from deep-sea hydrothermal-vent environments

To assess the physiological and phylogenetic diversity of culturable halophilic bacteria in deep-sea hydrothermal-vent environments, six isolates obtained from low-temperature hydrothermal fluids, sulfide rock and hydrothermal plumes in North and South Pacific Ocean vent fields located at 1530–2580 m depth were fully characterized. Three strains were isolated on media that contained oligotrophic concentrations of organic carbon (0·002 % yeast extract). Sequencing of the 16S rRNA gene indicated that all strains belonged to the genus Halomonas in the γ-subclass of the Proteobacteria. Consistent with previously described species, the novel strains were slightly to moderately halophilic and grew in media containing up to 22–27 % total salts. The isolates grew at temperatures as low as −1 to 2 °C and had temperature optima of 30 or 20–35 °C. Both the minimum and optimum temperatures for growth were similar to those of Antarctic and sea-ice Halomonas species and lower than typically observed for the genus as a whole. Phenotypic tests revealed that the isolates were physiologically versatile and tended to have more traits in common with each other than with closely related Halomonas species, presumably a reflection of their common deep-sea, hydrothermal-vent habitat of origin. The G+C content of the DNA for all strains was 56·0–57·6 mol%, and DNA–DNA hybridization experiments revealed that four strains (Eplume1T, Esulfide1T, Althf1T and Slthf2T) represented novel species and that two strains (Eplume2 and Slthf1) were related to Halomonas meridiana. The proposed new species names are Halomonas neptunia (type strain Eplume1T=ATCC BAA-805T=CECT 5815T=DSM 15720T), Halomonas sulfidaeris (type strain Esulfide1T=ATCC BAA-803T=CECT 5817T=DSM 15722T), Halomonas axialensis (type strain Althf1T=ATCC BAA-802T=CECT 5812T=DSM 15723T) and Halomonas hydrothermalis (type strain Slthf2T=ATCC BAA-800T=CECT 5814T=DSM 15725T).

Phylogenetic analysis of psychrophilic bacteria isolated from the Japan Trench, including a description of the deep-sea species Psychrobacter pacificensis sp. nov

Phylogenetic positions of psychrophilic bacteria isolated from the Japan Trench were determined by sequencing analysis of PCR-amplified bacterial small subunit (16S) rRNA genes. Between surface and deep-sea psychrophiles, distinct positions clearly differed within the gamma-Proteobacteria. In phylogenetic analysis using neighbour-joining, maximum-parsimony and maximum-likelihood, strains from surface seawater were inferred to be located in the Halomonas aquamarina-meridiana clade within the family Halomonadaceae. Strains from deep seawater (5000-6000 m), however, formed a novel monophyletic clade within the Moraxella-Psychrobacter branch in the family Moraxellaceae, showing separation from terrestrial and Antarctic relatives. These deep-sea strains were also discriminated from other known Psychrobacter species in phenotype, e.g. limited growth in the absence of NaCl (optimum at about 3% NaCl), positive urease activity, acid production from xylose and arabinose, and the presence of multiple fimbriae. DNA relatedness values among six deep-sea strains were > 85% in DNA-DNA hybridization experiments and > 98% in aligned 16S rDNA sequences. From this evidence, a new species, Psychrobacter pacificensis, is proposed for these deep-sea psychrophiles; the type strain of Psychrobacter pacificensis is strain NIBH P2K6T (= IFO 16270T). Occurrence of psychrobacters in cold Japan Trench deep seawater and at the Antarctic sea surface suggests that deep-sea bacterial habitation and evolution have been mediated by global deep-ocean circulation linked to the sinking of cooled seawater in polar regions.

Chromohalobacter salexigens sp. nov., a moderately halophilic species that includes Halomonas elongata DSM 3043 and ATCC 33174

Two strains that were originally isolated and characterized as members of the moderately halophilic species Halomonas elongata, strains DSM 3043 (= 1H11) and ATCC 33174 (= 1H15), were studied in detail. Their complete 16S rRNA sequences were determined and, when compared to sequences available from the databases, they showed a close phylogenetic relationship to Chromohalobacter marismortui. In addition, DNA-DNA hybridization experiments showed that both strains are members of the same species, but their DNA relatedness to the type strains of Halomonas elongata, ATCC 33173T, and Chromohalobacter marismortui, ATCC 17056T, is very low. Phenotypically, the two strains showed very similar features, related to those of Chromohalobacter, but clear differences were found between these two strains and Chromohalobacter marismortui. On the basis of these data, it is proposed that Halomonas elongata DSM 3043 and ATCC 33174 should be included in a new species of the genus Chromohalobacter, Chromohalobacter salexigens sp. nov. The type strain is DSM 3043T (= ATCC BAA-138T = CECT 5384T = CCM4921T = CIP106854T = NCIMB 13768T).

Halomonas ventosae sp. nov., a moderately halophilic, denitrifying, exopolysaccharide-producing bacterium

Halomonas ventosae sp, nov. includes three moderately halophilic, exopolysaccharide-producing strains isolated from saline soils in Jaén (south-eastern Spain). These strains can grow anaerobically using either nitrate or nitrite as terminal electron acceptor and hydrolyse both tyrosine and phenylalanine. Their G+C content varies between 72·6 and 74·3 mol%. The affiliation of the isolates with the genus Halomonas was confirmed by 16S rRNA gene sequence comparison. DNA–DNA hybridization shows 70·4–82·7 % relatedness among the three strains. Nevertheless, their relatedness is less than 43 % compared to related reference strains. The proposed type strain for Halomonas ventosae is strain Al12T (=CECT 5797T=DSM 15911T). It grows best at 8 % (w/v) sea salts and requires the presence of Na+. Its major fatty acids are 18 : 1 ω7c, 16 : 0, 16 : 1 ω7c, and 15 : 0 iso 2-OH. The predominant respiratory lipoquinone found in strain Al12T is ubiquinone with nine isoprene units (Q-9).

Halomonas maura sp. nov., a novel moderately halophilic, exopolysaccharide-producing bacterium

Four moderately halophilic, exopolysaccharide-producing bacterial strains isolated from soil samples collected from a saltern at Asilah (Morocco) are reported. These four strains were initially considered to belong to the genus Halomonas. Their DNA G+C contents varied between 62.2 and 64.1 mol %. DNA-DNA hybridization revealed a considerable degree of DNA-DNA similarity amongst all four strains (75.5-80.8%). Nevertheless, similarity with the reference strains of phylogenetically close relatives was lower than 40%. 16S rRNA gene sequences were compared with those of other species of Halomonas and other gram-negative bacteria and they were sufficiently distinct phylogenetically from other recognized Halomonas species to warrant their designation as a novel species. The name Halomonas maura sp. nov. is therefore proposed, with strain S-31T (= CECT 5298T= DSM 13445T) as the type strain. The fatty acid composition of strain S-31T revealed the presence of 18:1omega7c, 16:1omega7c/2-OH i15:0 and 16:0 as the major components. Growth rate analysis showed that strain S-31T had specific cationic requirements for Na+ and Mg2+.

Proposal of Cobetia marina gen. nov., comb. nov., within the family Halomonadaceae, to include the species Halomonas marina

At present the family Halomonadaceae consists of four genera and the taxonomic status of all species included in these genera is not equally supported by phylogenetic evidence. Whereas Zymobacter and Carnimonas contain one single species each and form the deeper branch of the family, the genus Halomonas contains currently 22 species, with a maximum 16S/23S rRNA sequence divergence greater than it could be expected for species of the same genus. In addition, we have witnessed during last years an increase in the number of new species within this group, which makes even more necessary a taxonomic rearrangement. In a previous study (Arahal et al., 2002) we evaluated the phylogenetic status of the family Halomonadaceae based on 23S and 16S rDNA sequence analyses and mentioned that Halomonas marina could eventually be assigned to a new genus. In this study we have emended the description of this species, including new features and propose its placement in a new genus, Cobetia gen. nov. within the family Halomonadaceae. The type strain of Cobetia marina is ATCC 25374T (= DSM 4741T). Further discussion on the phylogeny of the family Halomonadaceae is provided taking into account the most recent changes.

Halomonas boliviensis sp. nov., an alkalitolerant, moderate halophile isolated from soil around a Bolivian hypersaline lake

Halomonas boliviensis sp. nov. is proposed for two moderately halophilic, psychrophilic, alkalitolerant bacteria, LC1(T) (=DSM 15516(T)=ATCC BAA-759(T)) and LC2 (=DSM 15517=ATCC BAA-760), both of which were isolated from a soil sample around the lake Laguna Colorada, located at 4300 m above sea level in the south-west region of Bolivia. The bacteria are aerobic, motile, Gram-negative rods that produce colonies with a cream pigment. Moreover, they are heterotrophs that are able to utilize various carbohydrates as carbon sources. The organisms reduce nitrate and show tryptophan deaminase activity. The genomic DNA G+C contents were 51.4 mol% for isolate LC1(T) and 52.6 mol% for isolate LC2. Based on 16S rDNA sequence analysis, isolates LC1(T) and LC2 were identified as members of the genus Halomonas and clustered closely with Halomonas variabilis DSM 3051(T) and Halomonas meridiana DSM 5425(T). However, DNA-DNA relatedness between the new isolates and the closest related Halomonas species was low.

Halomonas campisalis sp. nov., a denitrifying, moderately haloalkaliphilic bacterium

The isolation and characterization of a denitrifying bacterium that is both moderately halophilic and alkaliphilic is described. The organism was isolated for use in the development of a bioprocess that could potentially reduce the costs of ion exchange resin regenerant disposal. The process of ion exchange, after resin regeneration, produces a briny, alkaline waste that is difficult and expensive to dispose. The biological removal of nitrate and subsequent reuse of these brines can potentially provide a cost-saving alternative to disposing of this waste product. To achieve our objective, a moderately halophilic, alkaliphilic bacterium was isolated from sediment samples taken from the salt plain of Alkali Lake in Washington State (USA). The haloalkaliphilic bacterium, designated strain 4A, is motile with rod-shaped cells that are 3 to 5 microm long and 1 microm wide. Electron acceptors used include oxygen, nitrate, and nitrite. In addition, it has similar specific nitrate reduction rates and biomass yields as non-halophilic denitrifying bacteria. It is capable of using a variety of electron donors. This organism can grow at NaCl concentrations ranging from 0.2 to 4.5 M with optimum growth occurring at 1.5 M and pH values ranging from 6 to 12 with 9.5 being the optimum pH. The temperature range for growth of strain 4A is 4-50 degrees C with optimal growth occurring at 30 degrees C. The G + C content is 66 mol%. Phylogenetic analyses based upon 16S rDNA gene sequence placed isolate 4A in the genus Halomonas. In addition, DNA-DNA hybridization experiments clearly indicate that it is a unique species. Phenotypic and phylogenetic studies indicate that isolate 4A represents a new species. We propose the name Halomonas campisalis for this species and strain 4A (ATCC 700597) as the type strain. Due to its denitrification ability, broad carbon utilization range and its high salinity and pH tolerance this organism, and similar ones, hold promise for the treatment of saline, alkaline waste.

Halomonas saccharevitans sp. nov., Halomonas arcis sp. nov. and Halomonas subterranea sp. nov., halophilic bacteria isolated from hypersaline environments of China

Three strains of Gram-negative, aerobic, neutrophilic and halophilic bacteria were isolated from samples of a salt lake on the Qinghai–Tibet Plateau and a subterranean saline well in the Si-Chuan Basin of China. These isolates, designated AJ275T, AJ282Tand ZG16T, were investigated using a polyphasic approach. Based on 16S rRNA gene sequence analysis, the isolates could be affiliated to the genusHalomonas. Genomic DNA G+C contents were 65.9 mol% for AJ275T, 56.7 mol% for AJ282Tand 57.6 mol% for ZG16T. The results of DNA–DNA hybridizations, fatty acid analysis and physiological and biochemical tests allowed the isolates to be differentiated genotypically and phenotypically from closely related species. It is proposed that strains AJ275T(=CGMCC 1.6493T=JCM 14606T=LMG 23976T), AJ282T(=CGMCC 1.6494T=JCM 14607T=LMG 23978T) and ZG16T(=CGMCC 1.6495T=JCM 14608T=LMG 23977T) represent the type strains of three novel species in the genusHalomonas:Halomonas saccharevitanssp. nov.,Halomonas arcissp. nov. andHalomonas subterraneasp. nov., respectively.

Transfer of Halomonas canadensis and Halomonas israelensis to the genus Chromohalobacter as Chromohalobacter canadensis comb. nov. and Chromohalobacter israelensis comb. nov

16S rRNA gene sequence comparisons and DNA-DNA hybridization data support the conclusion that two species previously described as members of the genus Halomonas, Halomonas israelensis and Halomonas canadensis, should be placed in the genus Chromohalobacter. Both H. israelensis ATCC 43985T (= Ba1T) and H. canadensis ATCC 43984T (= NRCC 41227T) have been used extensively for physiological studies for many years; nevertheless, they were not named and classified taxonomically until quite recently. Their phenotypic resemblance (at least 65% Jaccard similarity) to some members of the genus Halomonas and the degree of DNA-DNA relatedness (lower than 60%) to other described species of this genus permitted the conclusion that they were distinct species belonging to the genus Halomonas. In this study, the 16S rDNA of both species has been sequenced completely and found to share higher similarity to the available sequences of the moderately halophilic bacterium Chromohalobacter marismortui than to sequences of members of the genus Halomonas. C. marismortui is the sole species of the genus Chromohalobacter, also included in the family Halomonadaceae, and shares many phenotypic features with H. canadensis and H. israelensis. It is proposed that the two species should be renamed as Chromohalobacter canadensis comb. nov. and Chromohalobacter israelensis comb. nov. An emended description of the genus Chromohalobacter is given in order to include the features of these two species.

Halomonas shengliensis sp. nov., a moderately halophilic, denitrifying, crude-oil-utilizing bacterium

A moderately halophilic bacterium, designated strain SL014B-85T, was isolated from a crude-oil-contaminated saline soil from Shengli oilfield, Shandong Province, China. Cells were Gram-negative, aerobic, short rods with lateral flagella. Growth occurred at NaCl concentrations of 0–15 % (optimum 5–15 %), at 10–42 °C (optimum 30 °C) and at pH 8.0–9.0 (optimum pH 8.5). The only respiratory quinone was Q9, and the main cellular fatty acids were C18 : 1 ω7c, C16 : 0 and C19 : 0 cyclo ω8c. The G+C content of the DNA was 66.6 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain SL014B-85T belonged to the genus Halomonas in the Gammaproteobacteria, with highest sequence similarity of 98.1 and 97.8 % to Halomonas alimentaria DSM 15356T and Halomonas ventosae DSM 15911T, respectively. DNA–DNA relatedness values were below 40 % with members of closely related Halomonas species. Results of phenotypic, biochemical and phylogenetic analyses revealed that strain SL014B-85T could be classified as representing a novel species of the genus Halomonas, for which the name Halomonas shengliensis sp. nov. is proposed. The type strain is SL014B-85T (=CGMCC 1.6444T=LMG 23897T).

Halomonas alkaliantarctica sp. nov., isolated from saline lake Cape Russell in Antarctica, an alkalophilic moderately halophilic, exopolysaccharide-producing bacterium

The taxomony of strain CRSS (DSM 15686(T)=ATCC BAA-848(T)) isolated from Cape Russell in Antarctica (Ross Sea, 74 52.35 S 163 53.03 E) was investigated in a polyphasic approach. The morphological, physiological and genetic characteristics were compared with that of related species of the genus Halomonas. The isolate grew optimally at pH 9.0, 10% NaCl at 30 degrees C. The cells were Gram-negative aerobic rods able to produce exopolysaccharide. They accumulated glycine-betaine, as a major osmolyte, with minor components ectoine and glutamate. The strain CRSS biosynthetised alpha-glucosidase. The polar lipid profile consisted of phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol as major components. Ubiquinone with nine repetitive unities (Q9) was the only quinone found and the fatty acid composition was dominated by C18:1 (53%). The G+C content of DNA was 55.0mol% and its phylogenetic position was established by 16S rRNA gene sequencing as a member of the genus Halomonas. For physiological, chemotaxonomic and genetic features (DNA-DNA hybridisation) it is proposed to classify the isolate as a new species for which we propose the name Halomonas alkaliantarctica sp. nov.

Influence of high salinities on the degradation of diesel fuel by bacterial consortia

Microbial communities from three Argentinean saline soils were extracted and tested for their ability to degrade diesel fuel in liquid culture at salinities between 0% and 25%. In each case, the degradation process was continuously monitored by measuring oxygen consumption. Two communities (CR1 and CR2) showed nearly equal degrees of degradation across a salinity range of 0%–10% (the former degrading about 63% of the diesel fuel and the latter about 70% after 53 and 80 d, respectively). Furthermore, the degree of degradation was not significantly lower in the presence of 17.5% salt (58% and 65% degraded, respectively). A third community (El Zorro) showed a maximum turnover at 5% salt (79% diesel fuel degraded) and significant degradation (66%) at a salinity of 10%. However, the degree of degradation by this community clearly dropped at 0% and 15% salt. None of the communities were able to degrade diesel fuel in the presence of 25% salt, but the living cell counts showed that components of the microbial population survived the long-term exposure. The surviving portion is obviously sufficient to allow substantial restoration of the original community, as verified by the BIOLOG method. Isolates of the CR1 community were identified as members of the genera Cellulomonas, Bacillus, Dietzia, and Halomonas. In light of our investigations, the bioremediation of contaminated saline soils should be quite possible if the salinity of the soil water is lower than 15% or if it is reduced below this limit by the addition of water.Key words: salinity, diesel fuel, degradation, halotolerant and halophilic microorganisms, soil communities, diversity.

Halomonas alkaliphila sp. nov., a novel halotolerant alkaliphilic bacterium isolated from a salt pool in Campania (Italy)

A halotolerant and alkaliphilic Gram-negative bacterium, strain 18bAG(T), that grows aerobically at the optimum temperature of 37 degrees C, and at pH 7.5-10 (optimum 9.0), was isolated from a salt pool located in Montefredane in Campania Region (South of Italy). The isolate tolerated high concentration of NaCl up to 20%. Strain 18bAG(T) accumulated osmolytes and polyhydroxybutyrate, produced exopolysaccharide and possessed alpha-glucosidase activity. The predominant respiratory quinones were ubiquinones, Q8 and Q6(6H); phosphoethanolamine, phosphatidylglycerol and diphosphatidylglycerol were the predominant polar lipids. Major fatty acids were C16 : 1, C16 : 0, and C18 : 0. On the basis of 16S rRNA gene sequence similarity, 18bAG(T) was shown to belong to Halomonas genus. Analysis of 16S rRNA gene revealed a high similarity of strain 18bAG(T) to Halomonas venusta (DSM 4743(T)) and Halomonas hydrothermalis (DSM 15725(T)). Level of DNA-DNA relatedness between strain 18bAG(T) and the most related species Halomonas venusta and Halomonas hydrothermalis was 56.0% and 41.2%, respectively. The G+C content (mol%) of DNA was 53.0. The RiboPrinting patterns of Halomonas venusta and 18AG(T) showed a pattern similarity of 0.50. On the basis of genomic information and phenotypic characteristics strain 18bAG(T) represents a new species, for which the name Halomonas alkaliphila sp. nov. is proposed. The type strain is 18bAG(T) (=DSM 16354T =ATCC BAA-953T).

Halomonas campaniensis sp. nov., a haloalkaliphilic bacterium isolated from a mineral pool of Campania Region, Italy

A Gram-negative, aerobic, motile and rod-shaped haloalkaliphilic bacterial strain 5AGT (DSM 15293 and ATCC BAA-966) was isolated from water with algal mat of a mineral pool in Malvizza site (Campania-Italy) and was subjected to a polyphasic study. The isolate grew at temperature of 10.0-43.0 degrees C with an optimum at 37.0 degrees C. Strain 5AGT grew optimally in the presence of 10% NaCl and grew also in the absence of salt. The isolate grew in the pH range 7.0-10.0 with an optimum at pH 9.0. It accumulated glycine-betaine, ectoine, and glutamate, as osmoprotectants. Strain 5AGT was also characterized chemotaxonomically by having ubiquinone-8 (Q8) as the predominant isoprenoid quinone, phosphoethanolamine (PEA), phosphatidylglycerol (PG) and diphosphatidylglycerol (DPG), as major polar lipids and aiC16:0 and C18:1cis as the major fatty acids. The DNA G+C content was 63.7mol%. Phylogenetic analyses based on 16S rRNA gene sequence showed that the isolate belonged to the genus Halomonas. The DNA-DNA hybridization of the type strain 5AGT with the most related Halomonas campisalis showed a re-association value of 35.0%. On the basis of phenotypic properties and phylogeny, strain 5AGT should be placed in the genus Halomonas as a member of a novel species for which we propose the name Halomonas campaniensis sp. nov.

Halomonas gudaonensis sp. nov., isolated from a saline soil contaminated by crude oil

Two moderately halophilic strains, SL014B-69T and SL014B-62A2, were isolated from a saline soil contaminated with crude oil in Gudao in the coastal Shengli oilfield in China; the isolates were Gram-negative, rod-shaped and carried lateral flagella. Growth occurred at NaCl concentrations of 1–20 % (w/v), at temperatures of 10–42 °C and at pH 8.0–9.0. Strain SL014B-69T had C18 : 1 ω7c (28.61 %), C19 : 1 cyclo ω7c (27.97 %), C16 : 0 (19.66 %) and C12 : 0 3-OH (8.87 %) as the predominant fatty acids and Q9 as the major ubiquinone, with the G+C content of genomic DNA being 64.0 mol%. Phylogenetic analyses based on 16S rRNA gene sequences indicated that the two strains belonged to genus of Halomonas in the Gammaproteobacteria, with the highest 16S rRNA gene sequence similarities of 96.4 % with Halomonas campisalis ATCC 700597T and 96.0 % with Halomonas desiderata FB2T. DNA–DNA relatedness of strain SL014B-69T with strain SL014B-62A2, H. campisalis ATCC 700597T and H. desiderata DSM 9502T was 97.4, 42.9 and 36.8 %, respectively. On the basis of these data, a novel species of the genus Halomonas, Halomonas gudaonensis sp. nov., is proposed for strain SL014B-69T and SL014B-62A2. The type strain is SL014B-69T (=LMG 23610T=CGMCC 1.6133T).

Halomonas, a newly recognized human pathogen causing infections and contamination in a dialysis center: three new species

Our Renal Care Center (RCC) is a separate building, performing almost 2500 outpatient dialysis runs per month. In May 2007, 2 patients developed, days apart, bacteremia with an apparently identical nonfermentative Gram-negative rod. Because of difficulty identifying the organism, testing in the Biolog system identified them as a Halomonas species. Sequencing of approximately 1500 bases of the 16S rRNA gene in both organisms in 3 reference laboratories confirmed, searching against 3 databases, that the organisms were identical and were Halomonas species. There were 54 recognized species of this genus, associated with marine or saline sites. Initial attempts at environmental isolation as primary cultures, including a 4% salt agar plate, or initial incubation in 6.5% salt broth enrichment culture with subculture to agar, to exploit the halophilicity of Halomonas, were successful in demonstrating the colonies seen in the blood cultures, only from sites not contaminated with other organisms, because of competing growth. A more selective method was developed for use on samples suspected to be heavily contaminated with other organisms, using the strategy of increased salt concentration in a broth enrichment culture to further exploit Halomonas halotolerance, and thereby inhibit other organisms. A 16.5% salt concentration in brain-heart infusion broth, incubated at 35 degrees C for 48-72 hours, then subcultured to agar plates incubated in room air at 35 degrees C, proved optimal for selection and secondary isolation. With a combination of these techniques, 14/15 cultures of dialysates and 10/38 from the outflow pathways of the machines were Halomonas positive, compared to 0/31 cultures from the inflow side of the machines (including water supplies and storing, mixing, and preparation tanks). The exception was sites associated with or downstream of bicarbonate influx, 12/54 of which were positive. Two other local hospitals' dialysis centers, and our own inpatient dialysis facility, were cultured at sites that yielded Halomonas from our RCC, and Halomonas was not isolated. Further study by 16S rRNA gene sequencing and DNA-DNA hybridization revealed the cultures represented 3 novel species: 1 (H. stevensii sp. nov.) in the patients and environment and 2 (H. hamiltonii sp. nov., H. johnsoniae sp. nov.) in the environment, most closely related to H. magadiensis. Of 35 speciated isolates, 22 were H. stevensii, 10 H. johnsoniae, and 3 H. hamiltonii. We hypothesize that the RCC became contaminated with these halophilic organisms from bicarbonate used to prepare dialysis fluid, and they persist despite cleaning and flushing procedures because of biofilm in machines and bicarbonate fluid inflow sites. Our experience, together with the review of the literature presented here, indicates the genus Halomonas has pathogenic potential.

Halomonas gomseomensis sp. nov., Halomonas janggokensis sp. nov., Halomonas salaria sp. nov. and Halomonas denitrificans sp. nov., moderately halophilic bacteria isolated from saline water

A total of 34 Halomonas strains were isolated from saline water in Anmyeondo, Korea. Ten of these strains, considered to belong to novel species, were subjected to a polyphasic taxonomic investigation. The strains were Gram-negative, moderately halophilic, motile and non-spore-forming rods that contained Q-9 as the predominant ubiquinone and C18 : 1 ω7c, C16 : 0 and either summed feature 4 (C16 : 1 ω7c/C15 : 0 iso 2-OH) or C19 : 0 cyclo ω8c as the major fatty acids. Phylogenetic analysis, based on 16S rRNA gene sequencing, showed that the ten isolates formed four separate lineages in the genus Halomonas. Combined phenotypic data and DNA–DNA hybridization data supported the conclusion that they represent four novel species in the genus Halomonas, for which the names Halomonas gomseomensis sp. nov. (type strain M12T=KCTC 12662T=DSM 18042T), Halomonas janggokensis sp. nov. (type strain M24T=KCTC 12663T=DSM 18043T), Halomonas salaria sp. nov. (type strain M27T=KCTC 12664T=DSM 18044T) and Halomonas denitrificans sp. nov. (type strain M29T=KCTC 12665T=DSM 18045T) are proposed.

Quorum sensing in halophilic bacteria: detection of N-acyl-homoserine lactones in the exopolysaccharide-producing species of Halomonas

Some members of the moderately halophilic genus Halomonas, such as H. eurihalina, H. maura, H. ventosae and H. anticariensis, produce exopolysaccharides with applications in many industrial fields. We report here that these four species also produce autoinducer molecules that are involved in the cell-to-cell signaling process known as quorum sensing. By using the N-acyl homoserine lactone (AHL) indicator strains Agrobacterium tumefaciens NTL4 (pZRL4) and Chromobacterium violaceum CV026, we discovered that all the Halomonas strains examined synthesize detectable AHL signal molecules. The synthesis of these compounds was growth-phase dependent and maximal activity was reached during the late exponential to stationary phases. One of these AHLs seems to be synthesized only in the stationary phase. Some of the AHLs produced by H. anticariens FP35(T) were identified by gas chromatography/mass spectrometry and electrospray ionization tandem mass spectrometry as N-butanoyl homoserine lactone (C(4)-HL), N-hexanoyl homoserine lactone (C(6)-HL), N-octanoyl homoserine lactone (C(8)-HL) and N-dodecanoyl homoserine lactone (C(12)-HL). This study suggests that quorum sensing may also play an important role in extreme environments.

Halomonas anticariensis sp. nov., from Fuente de Piedra, a saline-wetland wildfowl reserve in Málaga, southern Spain

Three Halomonas strains, FP34, FP35T and FP36, which were isolated from soil samples taken from Fuente de Piedra, a saline wetland in the province of Málaga in southern Spain, are described. Phylogenetic analyses based on 16S rRNA gene sequences show that the three isolates belong to the genus Halomonas in the γ-Proteobacteria and form an independent genetic line. Phenotypically, they share the characteristics of Halomonas and differ from the most closely related species, Halomonas campisalis, in the following features: they are strictly aerobic and, because of their production of exopolysaccharides, form cream-coloured, mucoid colonies; they produce phosphatase and grow within narrow pH and temperature ranges; and they are susceptible to kanamycin and streptomycin. Their G+C content varies between 60·0 and 61·4 mol%. The name Halomonas anticariensis sp. nov. is proposed for these isolates. Strain FP35T (=LMG 22089T=CECT 5854T) is the type strain. The bacterium grows best in 7·5 % (w/v) NaCl and does not require magnesium or potassium salts for growth, although they do stimulate growth somewhat when present. Its major fatty acids are 18 : 1ω7c, 16 : 0, 16 : 1ω7c, 15 : 0 iso 2-OH, 12 : 0 3-OH, 12 : 0, 10 : 0 and 19 : 0 cyclo ω8c. Its predominant respiratory lipoquinone is ubiquinone with nine isoprene units (Q-9).

Extremely halophilic denitrifying bacteria from hypersaline inland lakes, Halovibrio denitrificans sp. nov. and Halospina denitrificans gen. nov., sp. nov., and evidence that the genus name Halovibrio Fendrich 1989 with the type species Halovibrio variabilis should be associated with DSM 3050

Anaerobic enrichments with acetate as electron donor and nitrate as electron acceptor at 4 M NaCl from inland, hypersaline lake sediments from Central Asia resulted in the isolation of several extremely halophilic bacteria that comprised two subgroups, most with vibrio-shaped cells and a single strain with rod-shaped cells. Members of both subgroups were extremely halophilic, with growth occurring in 2–5 M NaCl with an optimum at 2–3 M. 16S rRNA gene sequence analysis showed a close affiliation of the new isolates with Pseudomonas halophila DSM 3050 in the Gammaproteobacteria. However, phenotypic comparison of the denitrifying halophiles with the original description of P. halophila demonstrated that they were more similar to another bacterium isolated from the same source at the same time, the extremely halophilic Halovibrio variabilis, which has since been reclassified as Halomonas variabilis (DSM 3051). Direct cross-comparison showed that the characteristics of these two halophilic bacteria do not correspond with the original descriptions associated with these names and DSM numbers. While it is desirable that this problem be solved, in connection with the present investigations, this is a matter that can only be solved by a Request for an Opinion. On the basis of the phenotypic and genetic comparison of these isolates, it is proposed that the new denitrifying vibrio-shaped isolates represent a novel species, Halovibrio denitrificans sp. nov. (type strain HGD 3T=DSM 15503T=UNIQEM U232T) and that the rod-shaped isolate represents a novel genus and species, Halospina denitrificans gen. nov., sp. nov. (type strain HGD 1-3T=DSM 15505T=UNIQEM U233T).