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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 gamma-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 degrees C and had temperature optima of 30 or 20-35 degrees 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 (Eplume1(T), Esulfide1(T), Althf1(T) and Slthf2(T)) 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 Eplume1(T)=ATCC BAA-805(T)=CECT 5815(T)=DSM 15720(T)), Halomonas sulfidaeris (type strain Esulfide1(T)=ATCC BAA-803(T)=CECT 5817(T)=DSM 15722(T)), Halomonas axialensis (type strain Althf1(T)=ATCC BAA-802(T)=CECT 5812(T)=DSM 15723(T)) and Halomonas hydrothermalis (type strain Slthf2(T)=ATCC BAA-800(T)=CECT 5814(T)=DSM 15725(T)).

DNA, Bacterial↗

Description of two new species of Halomonas: Halomonas israelensis sp.nov. and Halomonas canadensis sp.nov.

Six well-known strains of halotolerant bacteria, including two strains previously identified only as NRCC 41227 and Ba1, have been compared using 125 phenotypic characters and DNA-DNA hybridization. Although these strains represent some of the most heavily studied salt-tolerant bacteria, they have never been taxonomically compared. The data presented show that these bacteria form a relatively homogeneous group related at the genus level. The taxonomic comparison showed that these six organisms represented four distinct species all related above the 65% Jaccard coefficient level. In addition to two previously identified bacterial species, Halomonas elongata (ATCC 33173T) and Halomonas halodurans (ATCC 29686T), the strains included in this study represent two previously unnamed Halomonas species. These two new taxa have been assigned the names Halomonas israelensis (ATCC 43985T) and Halomonas canadensis (NRCC 41227T = ATCC 43984). DNA-DNA hybridization show that these two species are related to the type species H. elongata at 54.9 and 48.9%, respectively.

Culture Media↗

Halomonas magadii sp. nov., a new member of the genus Halomonas, isolated from a soda lake of the East African Rift Valley.

A number of novel alkaliphilic organotrophic bacteria have been isolated from several saline and alkaline East African soda lakes. The new isolates grow at pH values between 7.0 and 11.0, with pH optima for growth between 9.0 and 10.0. Growth occurs at total salts concentration between 0% and 20% (w/v) with optimum at 0%-7% (w/v). Phylogenetic analyses based on 16S rDNA sequence comparison indicate that these isolates are related (>96% similarity) to members of the Halomonadaceae within the gamma-3 subdivision of the Proteobacteria. These analyses indicate that existing species within the Halomonadaceae fell within three main groups, one group comprising the type species of Halomonas, Halomonas elongata, and a number of other known species including one soda lake isolate. A second group constituting most of the remaining known species of Halomonas and related Chromohalobacter spp. includes 3 soda lake isolates with high DNA-DNA homologies. The third group included Halomonas halodenitrificans, Halomonas desiderata, Halomonas cupida, and 13 soda lake isolates. Phenotypic comparisons indicated that the majority of soda lake strains shared similar morphological, phenotypic, and chemotaxonomic properties to known strains of Halomonas but grew under alkaline conditions. The 3 soda lake isolates with high DNA-DNA homologies were, however, significantly different in antibiotic sensitivity pattern and in the utilization of several substrates, were unable to reduce nitrite, and showed low DNA-DNA homologies with known halomonads in the same group. We propose that these isolates comprise a new species of the genus Halomonas that we name Halomonas magadii sp. nov. The type strain is strain 21 MI (NCIMB 13595).

Africa↗

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.

DNA, Bacterial↗

Exopolysaccharides produced by the recently described halophilic bacteria Halomonas ventosae and Halomonas anticariensis.

We studied exopolysaccharides (EPSs) produced by Halomonas ventosae and Halomonas anticariensis, two novel species of halophilic bacteria. Under optimum environmental and nutritional conditions, H. ventosae strains Al12(T) and Al16 excreted 28.35 mg and 28.95 mg of EPS per 100 ml of culture medium (34.55 and 38.6 mg of EPS per gram of dry cell weight) respectively. The molecular masses of the polymers were about 50 kDa and their main components were glucose, mannose and galactose. They had high protein fractions and showed emulsifying activity on several hydrophobic substrates. Under optimum environmental and nutritional conditions, H. anticariensis strains FP35(T) and FP36 excreted about 29.65 and 49.95 mg of EPS per 100 ml of culture medium (43.6 and 50.95 mg of EPS per gram of dry cell weight) respectively. The molecular masses of the polymers were about 20 and 46 kDa respectively and were composed mainly of glucose, mannose and galacturonic acid. All EPSs produced solutions of low viscosity and pseudoplastic behaviour. They also had a high capacity for binding cations and incorporated considerable quantities of sulphates, which is highly unusual in bacterial polysaccharides. All strains assayed formed biofilms both in polystyrene wells and borosilicate test tubes.

Biofilms↗

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.

Animals↗

Phylogenetic inferences and taxonomic consequences of 16S ribosomal DNA sequence comparison of Chromohalobacter marismortui, Volcaniella eurihalina, and Deleya salina and reclassification of V. eurihalina as Halomonas eurihalina comb. nov.

The phylogenetic positions of the moderately halophilic bacteria Chromohalobacter marismortui, Volcaniella eurihalina, and Deleya salina were determined by PCR amplification of rRNA genes and direct sequencing. The resulting data were compared with data for other bacteria obtained from 16S rRNA sequence databases. C. marismortui, V. eurihalina, and D. salina clustered phylogenetically within the gamma subclass of the Proteobacteria and are closely related to other species on the Halomonas-Deleya branch. C. marismortui belongs in the family Halomonadaceae and has the characteristic 16S rRNA signatures defined for this family, including the distinctive cytosine residue at position 486 found in all members of the Halomonadaceae. V. eurihalina is closely related to the type species of the genus Halomonas, Halomonas elongata, and we formally propose that V. eurihalina should be transferred to the genus Halomonas as Halomonas eurihalina comb. nov. The type strain of this species is strain F9-6 (= ATCC 49336). D. salina is not as closely related to other species belonging to the Halomonas-Deleya complex, but is more closely related to Halomonas elongata than to Deleya aquamarina, the type species of the genus Deleya. A polyphasic approach will be necessary to determine the natural taxonomic positions of the species belonging to the genera Halomonas and Deleya, as well as C. marismortui, V. eurihalina, Halovibrio variabilis, and Paracoccus halodenitrificans.

Base Sequence↗

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.

Bacterial Typing Techniques↗

Halomonas marisflavae sp. nov., a halophilic bacterium isolated from the Yellow Sea in Korea.

A halophilic Gram-negative bacterial strain, SW32T, which was isolated from a sample from the Yellow Sea of Korea, was subjected to a polyphasic taxonomic study. This organism grew optimally in the presence of 0.5-12% NaCl. On the basis of phenotypic and phylogenetic data, strain SW32T appeared to be a member of the genus Halomonas. Strain SW32T formed a distinct evolutionary lineage within the phylogenetic clade comprising Halomonas species and the genera Zymobacter and Carnimonas. The 16S rDNA sequence of strain SW32T contains 19 signature characteristics of the genus Halomonas and the family Halomonadaceae. Strain SW32T possessed a single polar flagellum, ubiquinone-9 as the predominant respiratory lipoquinone and C18:1, C16:0 and C16:1 omega7c and/or iso-C15:0 20H as the major fatty acids. The DNA G+C content was 59 mol%. Levels of 16S rDNA similarity between strain SW32T and the type strains of all validly described Halomonas species were 92.0-93.8%. Strain SW32T exhibited 16S rDNA similarity values of 92.7% to Zymobacter palmae IAM 14233T and 91.6% to Carnimonas nigrificans CECT 4437T. These data indicate that strain SW32T was related enough to members of the genus Halomonas to be placed as a new species within that genus. Therefore the name Halomonas marisflavae sp. nov. is proposed for strain SW32T. The type strain of the new species is strain SW32T (= KCCM 80003T = JCM 10873T).

DNA, Ribosomal↗

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.

Aminosalicylic Acid↗

Halomonas taeanensis sp. nov., a novel moderately halophilic bacterium isolated from a solar saltern in Korea.

A moderately halophilic, Gram-negative bacterium, strain BH539(T), which was isolated from a solar saltern at Taean in Korea, was considered to be a member of the genus Halomonas. Strain BH539(T) grew at salinities of 1-25% (w/v) and at temperatures of 10-45 degrees C. Cells were short rods that were motile by means of several flagella. Their major fatty acids were C(18:1)omega7c, C(16:0) and C(19:0) cyclo omega8c. The genomic DNA G+C content was about 65 mol% and the predominant ubiquinone was Q-9. Phylogenetic analyses based on 16S rRNA gene sequences indicated that the isolate formed a branch of the species Cobetia marina. However, 23S and 16S rRNA gene sequence similarities revealed that strain BH539(T) was related more closely to the type strains of the genus Halomonas. Phylogenetic analyses based on 23S rRNA gene sequences also indicated that the strain formed a phyletic line within the genus Halomonas. Therefore, it was concluded that strain BH539(T) should be classified within the genus Halomonas, rather than Cobetia. On the basis of physiological and molecular properties, strain BH539(T) represents a novel species of the genus Halomonas, for which the name Halomonas taeanensis sp. nov. is proposed. The type strain is BH539(T) (=KCTC 12284(T)=DSM 16463(T)).

Bacterial Typing Techniques↗

Phylogenetic relationships between some members of the genera Deleya, Halomonas, and Halovibrio.

The genera Halomonas and Deleya, which constitute the family Halomonadaceae, are difficult to differentiate on the basis of phenotypic and chemotaxonomic attributes. DNA-rRNA hybridization studies have indicated that some Halomonas spp. have the same level of relationship to the type species of the genus Deleya as some Deleya spp. A phylogenetic analysis of the 16S rRNA sequences of seven members of the Halomonadaceae indicated that the members of the genera Halomonas and Deleya do not form separate monophyletic subgroups, confirming the lack of any phylogenetic support for retention of these taxa as separate genera. A phylogenetic analysis of the 16S rRNA sequence of Halovibrio variabilis confirmed that this species belongs in the Halomonadaceae. All of the members of the Halomonadaceae examined and Halovibrio variabilis possess a cytosine residue at position 486 (Escherichia coli numbering), which is an extremely rare attribute among the prokaryotes and has been reported in only one other species, Listonella anguillarum. Several other signature characteristics which define this group in the gamma subclass of the Proteobacteria are identified. The Jukes-Cantor distances between members of the family Halomonadaceae, including Halovibrio variabilis, range from 0.086 to 0.000 (the levels of similarity between the 16S rRNA sequences range from 92.6 to 100%). The members of the genera Halomonas, Deleya, and Halovibrio form a monophyletic group and share common chemotaxonomic and phenotypic characteristics. Subgroups containing members of the genera Halomonas, Deleya, and Halovibrio cannot be resolved on the basis of phylogenetic, chemotaxonomic, or phenotypic data. Our data indicate that the members of the genera Halomonas, Deleya, and Halovibrio should be united in a single genus.

Biological Evolution↗

Halomonas glaciei sp. nov. isolated from fast ice of Adelie Land, Antarctica.

Eleven psychrophilic bacteria were isolated from a solid layer of fast ice in the middle of Pointe-Geologie Archipelago, Adelie Land, Antarctica. The 11 isolates based on the phenotypic characteristics, chemotaxonomic and phylogenetic analysis have been identified as members of the genus Halomonas. All the isolates at the 16S rDNA sequence level were identical, possessed the 15 conserved nucleotides of the family Halomonadaceae and four nucleotides of the genus Halomonas. Therefore, the 16S rDNA sequence of DD 39 was used for calculating the evolutionary distances and for phylogenetic analysis. It was observed that DD 39 formed a robust cluster with H. variabilis, from which it differed by 0.7%. Further DNA-DNA hybridization studies indicated low DNA-DNA homology (15%) between H. variabilis and DD 39. Between the 11 Antarctic isolates the homology was >85%. In addition it was observed that DD 39 was different from H. variabilis in that it was psychrophilic, could tolerate only up to 15% sodium chloride, could not hydrolyse esculin, could not reduce nitrate, was urease negative, could not utilize glycerol as a carbon source, and was resistant to ampicillin and erythromycin and sensitive to nalidixic acid. In addition, it also exhibited distinct differences with respect to high content of C(16:1) and low levels of cyclo-C(17:0) and cyclo-C(19:0). DD 39 also differed from all the other reported species of Halomonas with respect to many phenotypic characteristics. It is proposed therefore that DD 39 should be placed in the genus Halomonas as a new species that is Halomonas glaciei. The type strain of H. glaciei is DD 39(T) (MTCC 4321; JCM 11692).

Antarctic Regions↗

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.

Base Composition↗

Halomonas anticariensis sp. nov., from Fuente de Piedra, a saline-wetland wildfowl reserve in Malaga, 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 gamma-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 : 1omega7c, 16 : 0, 16 : 1omega7c, 15 : 0 iso 2-OH, 12 : 0 3-OH, 12 : 0, 10 : 0 and 19 : 0 cyclo omega8c. Its predominant respiratory lipoquinone is ubiquinone with nine isoprene units (Q-9).

Aerobiosis↗

Halomonas koreensis sp. nov., a novel moderately halophilic bacterium isolated from a solar saltern in Korea.

A moderately halophilic bacterium, strain SS20(T), capable of growing at salinities of 1-20 % (w/v) NaCl was isolated from a solar saltern of the Dangjin area in Korea and was characterized taxonomically. Strain SS20(T) was a Gram-negative bacterium comprising motile, short rods. Its major cellular fatty acids were C(18 : 1)omega7c, C(19 : 0)omega8c cyclo and C(16 : 0). The DNA G+C content was 70 mol% and the predominant ubiquinone was Q-9. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain SS20(T) belonged to the genus Halomonas. The levels of 16S rRNA gene sequence similarity to the type strains of Halomonas species were in the range 93.0-97.5 %. The levels of DNA-DNA relatedness between strain SS20(T) and the type strains of phylogenetically closely related Halomonas species were in the range 5.3-12.3 %. On the basis of physiological and molecular properties, strain SS20(T) represents a novel species of the genus Halomonas, for which the name Halomonas koreensis sp. nov. is proposed. The type strain is SS20(T) (=KCTC 12127(T)=JCM 12237(T)).

Bacterial Typing Techniques↗

Halomonas almeriensis sp. nov., a moderately halophilic, exopolysaccharide-producing bacterium from Cabo de Gata, Almería, south-east Spain.

Halomonas almeriensis sp. nov. is a Gram-negative non-motile rod that was isolated from a saltern in the Cabo de Gata-Níjar wildlife reserve in Almería, south-east Spain. It is moderately halophilic, capable of growth at concentrations of 5-25% w/v sea-salt mixture, the optimum being 7.5% w/v. It is chemo-organotrophic and strictly aerobic, produces catalase but not oxidase, does not produce acid from any sugar and does not synthesize hydrolytic enzymes. The most notable difference between this micro-organism and other Halomonas species is that it is very fastidious in its use of a carbon source. It forms mucoid colonies due to the production of an exopolysaccharide. Its G+C content is 63.5 mol%. A comparison of 16S rRNA gene sequences confirmed its relationship to Halomonas species. The most closely related species is Halomonas halmophila with 95.8% similarity between their 16S rRNA gene sequences. DNA-DNA hybridization with H. halmophila is 10.1%. Its major fatty acids are 18:1omega7c, 16:0, 16:1omega7c/15:0 iso 2-OH, 12:0 3-OH, 12:0, 11-methyl 18:1omega7c and 10:0. The proposed name is Halomonas almeriensis sp. nov., with strain M8(T) (=CECT 7050(T)=LMG 22904(T)) as the type strain.

Aerobiosis↗

Major outer membrane proteins in moderately halophilic eubacteria of genera Chromohalobacter and Halomonas.

Outer and inner membrane fractions of Chromohalobacter marismortui and Halomonas elongata were isolated by differential detergent solubilization, and profiles of membrane proteins, especially major outer membrane proteins, were analyzed. These type strains possessed one extremely abundant outer membrane protein which showed similarity in amino-terminal amino acid sequence with the outer membrane porin proteins in other Gram-negative bacteria. Three halophilic eubacterial strains isolated from saline environments were also characterized. Strains 160 and 43 were found to be Chromohalobacter spp. and strain 40 to be a Halomonas sp. by sequence analysis of their 16 S ribosomal RNA genes. Extremely abundant porin proteins with an apparent molecular mass of 49 kDa were found in Chromohalobacter sp.160 and Halomonas sp. 40, but no major outer membrane protein was detected in Chromohalobacter sp. 43, suggesting strain 43 was most likely a naturally defective porin mutant. Porin proteins from Chromohalobacter spp. and Halomonas spp. showed the same migration on SDS-polyacrylamide gel electrophoresis with or without heat-treatment, indicating that these porin proteins did not form a SDS-resistant trimeric structure, which was detected in most of the Gram-negative bacterial porin proteins.

Amino Acid Sequence↗