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PubMed2005

Discrepancies in the widely applied GAM42a fluorescence in situ hybridisation probe for Gammaproteobacteria.

A bacterial culture collection of 104 strains was obtained from an activated sludge wastewater treatment plant to pursue studies into microbial flocculation. Characterisation of the culture collection using a polyphasic approach indicated seven isolates, phylogenetically affiliated with the deep-branching Xanthomonas group of the class Gammaproteobacteria, were unable to hybridise the GAM42a fluorescence in situ hybridisation (FISH) probe for Gammaproteobacteria. The sequence of the GAM42a probe target region in the 23S rRNA gene of these isolates was determined to have mismatches to GAM42a. Probes perfectly targeting the mismatches (GAM42a_T1038_G1031, and GAM42a_T1038 and GAM42a_A1041_A1040) were synthesised, and used in conjunction with GAM42a in FISH to study the Gammaproteobacteria community structure in one full-scale activated sludge plant. Several bacteria in the activated sludge biomass bound the modified probes demonstrating their presence and the fact that these Gammaproteobacteria have been overlooked in community structure analyses of activated sludge.

Gammaproteobacteria↗

PubMed2004

Cultivation and growth characteristics of a diverse group of oligotrophic marine Gammaproteobacteria.

Forty-four novel strains of Gammaproteobacteria were cultivated from coastal and pelagic regions of the Pacific Ocean using high-throughput culturing methods that rely on dilution to extinction in very low nutrient media. Phylogenetic analysis showed that the isolates fell into five rRNA clades, all of which contained rRNA gene sequences reported previously from seawater environmental gene clone libraries (SAR92, OM60, OM182, BD1-7, and KI89A). Bootstrap analyses of phylogenetic reliability did not support collapsing these five clades into a single clade, and they were therefore named the oligotrophic marine Gammaproteobacteria (OMG) group. Twelve cultures chosen to represent the five clades were successively purified in liquid culture, and their growth characteristics were determined at different temperatures and dissolved organic carbon concentrations. The isolates in the OMG group were physiologically diverse heterotrophs, and their physiological properties generally followed their phylogenetic relationships. None of the isolates in the OMG group formed colonies on low- or high-nutrient agar upon their first isolation from seawater, while 7 of 12 isolates that were propagated for laboratory testing eventually produced colonies on 1/10 R2A agar. The isolates grew relatively slowly in natural seawater media (1.23 to 2.63 day(-1)), and none of them grew in high-nutrient media (>351 mg of C liter(-1)). The isolates were psychro- to mesophilic and obligately oligotrophic; many of them were of ultramicrobial size (<0.1 micro m(3)). This cultivation study revealed that sporadically detected Gammaproteobacteria gene clones from seawater are part of a phylogenetically diverse constellation of organisms mainly composed of oligotrophic and ultramicrobial lineages that are culturable under specific cultivation conditions.

Bacteriological Techniques↗

PubMed2006

Rheinheimera perlucida sp. nov., a marine bacterium of the Gammaproteobacteria isolated from surface water of the central Baltic Sea.

A bacterial isolate from the Baltic Sea, BA131(T), was characterized for its physiological and biochemical features, fatty acid profile, G+C content and phylogenetic position based on comparative 16S rRNA gene sequence analysis. The strain was isolated from surface water of the central Baltic Sea during the decay of a plankton bloom. Phylogenetic analyses of the 16S rRNA gene sequence revealed a clear affiliation with the Gammaproteobacteria, and showed closest phylogenetic relationships with the genera Alishewanella and Rheinheimera. The G+C content of the DNA of strain BA131(T) was 48.9 mol%. Cells were non-pigmented, Gram-negative, rod-shaped, motile by means of a single polar flagellum and catalase- and oxidase-positive. Growth was observed at salinities from 0 to 8 %, with an optimum at 1-3 %. Temperature for growth ranged from 4 to 37 degrees C, with an optimum around 25 degrees C. The fatty acids were dominated by 16 : 0 (17-18 %) and by unsaturated compounds (>61 % of the total): 16 : 1omega7c (24-33 %), 17 : 1omega8c (14-18 %) and 18 : 1omega7c (9-12 %). Based on the data presented, BA131(T) is proposed as the type strain of a novel species of the genus Rheinheimera, Rheinheimera perlucida sp. nov. The type strain is BA131(T) (=LMG 23581(T)=CIP 109200(T)).

Baltic States↗

PubMed2005

New gammaproteobacteria associated with blood-feeding leeches and a broad phylogenetic analysis of leech endosymbionts.

Many monophagous animals have coevolutionary relationships with bacteria that provide unavailable nutrients to the host. Frequently, these microbial partners are vertically inherited and reside in specialized structures or tissues. Here we report three new lineages of bacterial symbionts of blood-feeding leeches, one from the giant Amazonian leech, Haementeria ghilianii, and two others from Placobdelloides species. These hosts each possess a different mycetome or esophageal organ morphology where the bacterial cells are located. DNA sequencing of the bacterial 16S rRNA genes and fluorescent in situ hybridization placed these symbionts in two separate clades in the class Gammaproteobacteria. We also conducted a broad phylogenetic analysis of the herein-reported DNA sequences as well as others from bacterial symbionts reported elsewhere in the literature, including alphaproteobacterial symbionts from the leech genus Placobdella as well as Aeromonas veronii from the medicinal leech, Hirudo medicinalis, and a Rickettsia sp. detected in Hemiclepsis marginata. Combined, these results indicate that blood-feeding leeches have forged bacterial partnerships at least five times during their evolutionary history.

Animals↗

PubMed2002

The genus Caedibacter comprises endosymbionts of Paramecium spp. related to the Rickettsiales (Alphaproteobacteria) and to Francisella tularensis (Gammaproteobacteria).

Obligate bacterial endosymbionts of paramecia able to form refractile inclusion bodies (R bodies), thereby conferring a killer trait upon their ciliate hosts, have traditionally been grouped into the genus CAEDIBACTER: Of the six species described to date, only the Paramecium caudatum symbiont Caedibacter caryophilus has been phylogenetically characterized by its 16S rRNA gene sequence, and it was found to be a member of the Alphaproteobacteria related to the RICKETTSIALES: In this study, the Caedibacter taeniospiralis type strain, an R-body-producing cytoplasmatic symbiont of Paramecium tetraurelia strain 51k, was investigated by comparative 16S rRNA sequence analysis and fluorescence in situ hybridization with specific oligonucleotide probes. C. taeniospiralis is not closely related to C. caryophilus (80% 16S rRNA sequence similarity) but forms a novel evolutionary lineage within the Gammaproteobacteria with the family Francisellaceae as a sister group (87% 16S rRNA sequence similarity). These findings demonstrate that the genus Caedibacter is polyphyletic and comprises at least two phylogenetically different bacterial species belonging to two different classes of the PROTEOBACTERIA: Comparative phylogenetic analysis of C. caryophilus, five closely related Acanthamoeba endosymbionts (including one previously uncharacterized amoebal symbiont identified in this study), and their hosts suggests that the progenitor of the alphaproteobacterial C. caryophilus lived within acanthamoebae prior to the infection of paramecia.

Acanthamoeba↗

PubMed2006

Thorsellia anophelis gen. nov., sp. nov., a new member of the Gammaproteobacteria.

A Gram-negative, rod-shaped organism (CCUG 49520T) was isolated from the midgut of the mosquito Anopheles arabiensis. 16S rRNA gene sequence analysis demonstrated that this isolate is unique, showing <93% similarity to species of the families Enterobacteriaceae and Vibrionaceae. The quinone system consisted exclusively of ubiquinone Q-8; the polar lipid profile consisted of the major compounds phosphatidylethanolamine and phosphatidylglycerol, a moderate to minor amount of two unknown aminophospholipids, an unknown phospholipid and two unknown polar lipids; the polyamine pattern was characterized by the predominant compound 1,3-diaminopropane and showed some significant differences when compared with members of the Enterobacteriaceae and Vibrionaceae. On the basis of 16S rRNA gene sequence analysis in combination with chemotaxonomic data, strain CCUG 49520T is considered to represent a new genus and species, for which the name Thorsellia anophelis gen. nov., sp. nov. is proposed. The type strain is CCUG 49520T (=CIP 108754T).

Animals↗

PubMed2006

Ferrimonas futtsuensis sp. nov. and Ferrimonas kyonanensis sp. nov., selenate-reducing bacteria belonging to the Gammaproteobacteria isolated from Tokyo Bay.

Two novel mesophilic, facultatively anaerobic, selenate-reducing bacteria, designated strains FUT3661T and Asr22-7T, were isolated from a sediment sample and the alimentary tract of littleneck clams, respectively. Both sources of the samples were collected from the coast of Tokyo Bay, Japan. Cells were Gram-negative rods and motile by means of a polar flagellum. The strains reduced selenate to elemental selenium (Se0) and also reduced iron(III) oxyhydroxide, iron(III) citrate, arsenate, manganese(IV) oxide, elemental sulfur and oxygen and used lactate, pyruvate, yeast extract, tryptone and Casamino acids as electron donors and carbon sources. The strains contained both menaquinone (MK-7) and ubiquinones (Q-7 and Q-8) as isoprenoid quinones. The major fatty acids were C16:0 and C16:1omega9c. The G+C content of the genomic DNA was 58.1 mol% for strain FUT3661T and 57.2 mol% for strain Asr22-7T. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the strains were related to members of the genus Ferrimonas (<94.0% similarities), although the two novel strains formed a separate lineage. 16S rRNA gene sequence similarity between strains FUT3661T and Asr22-7T was 96%. On the basis of this polyphasic analysis, it was concluded that strains FUT3661T and Asr22-7T represent two novel species within the genus Ferrimonas, for which the names Ferrimonas futtsuensis sp. nov. (type strain FUT3661T=NBRC 101558T=DSM 18154T) and Ferrimonas kyonanensis sp. nov. (type strain Asr22-7T=NBRC 101286T=DSM 18153T) are proposed.

Amino Acids↗

PubMed2003

Limitations of the widely used GAM42a and BET42a probes targeting bacteria in the Gammaproteobacteria radiation.

The 23S rRNA-targeted probes GAM42a and BET42a provided equivocal results with the uncultured gammaproteobacterium 'Candidatus Competibacter phosphatis' where some cells bound GAM42a and other cells bound BET42a in fluorescence in situ hybridization (FISH) experiments. Probes GAM42a and BET42a span positions 1027-1043 in the 23S rRNA and differ from each other by one nucleotide at position 1033. Clone libraries were prepared from PCR products spanning the 16S rRNA genes, intergenic spacer region and 23S rRNA genes from two mixed cultures enriched in 'Candidatus C. phosphatis'. With individual clone inserts, the 16S rDNA portion was used to confirm the source organism as 'Candidatus C. phosphatis' and the 23S rDNA portion was used to determine the sequence of the GAM42a/BET42a probe target region. Of the 19 clones sequenced, 8 had the GAM42a probe target (T at position 1033) and 11 had G at position 1033, the only mismatch with GAM42a. However, none of the clones had the BET42a probe target (A at 1033). Non-canonical base-pairing between the 23S rRNA of 'Candidatus C. phosphatis' with G at position 1033 and GAM42a (G-A) or BET42a (G-T) is likely to explain the probing anomalies. A probe (GAM42_C1033) was optimized for use in FISH, targeting cells with G at position 1033, and was found to highlight not only some 'Candidatus C. phosphatis' cells, but also other bacteria. This demonstrates that there are bacteria in addition to 'Candidatus C. phosphatis' with the GAM42_C1033 probe target and not the BET42a or GAM42a probe target.

Betaproteobacteria↗

PubMedDate not supplied

[Phylogenetic characterization of endosymbionts of the hydrothermal vent mussel Bathymodiolus azoricus by analysis of the 16S rRNA, pmoL, and cbbA genes].

In order to assess the phylogenetic diversity of the endosymbiotic microbial community of the gills of marine shellfish Bathymodiolus azoricus, total DNA was extracted from the gills. The PCR fragments corresponding to the genes encoding 16S rRNA, ribulose-bisphosphate carboxylase (cbbL), and particulate methane monooxygenase (pmoA) were amplified, cloned, and sequenced. For the 16S rDNA genes, only one phylotype was revealed; it belonged to the cluster of Mytilidae thiotrophic symbionts within the Gammaproteobacteria. For the RuBisCO genes, two phylotypes were found, both belonging to Gammaproteobacteria. One of them was closely related to the previously known mytilid symbiont, the other, to a pogonophore symbiont, presumably a methanotrophic bacterium. One phylotype of particulate methane oxygenase genes was also revealed; this finding indicated the presence of a methanotrophic symbiont. Phylogenetic analysis of the pmoA placed this endosymbiont within the Gammaproteobacteria, in a cluster including the methanotrophic bacterial genus Methylobacter and other methanotrophic Bathymodiolus gill symbionts. These results provide evidence for the existence of two types of endosymbionts (thioautotrophic and methanotrophic) in the gills of B. azoricus and demonstrate that, apart from the phylogenetic analysis of 16S rRNA genes, parallel analysis of functional genes is essential.

Animals↗

PubMed2005

Chemolithotrophic haloalkaliphiles from soda lakes.

This paper summarizes recent data on the occurrence and properties of lithotrophic prokaryotes found in extremely alkaline, saline (soda) lakes. Among the chemolithotrophs found in these lakes the obligately autotrophic sulfur-oxidizing bacteria were the dominant, most diverse group, best adapted to haloalkaline conditions. The culturable forms are represented by three new genera, Thioalkalimicrobium, Thioalkalivibrio and Thioalkalispira in the Gammaproteobacteria. Among them, the genus Thioalkalivibrio was most metabolically diverse, including denitrifying, thiocyanate-oxidizing and facultatively alkaliphilic species. Culturable methane-oxidizing populations in the soda lakes belong to the type I methanotroph group in the Gammaproteobacteria, mostly in the genus Methylomicrobium. The nitrifying bacteria in hyposaline soda lakes were represented by a new species Nitrobacter alkalicus (Alphaproteobacteria), and by an alkaliphilic subspecies of Nitrosomonas halophila (Betaproteobacteria). Both belonged to the low salt-tolerant alkaliphiles. The facultatively autotrophic haloalkaliphilic isolates able to grow with hydrogen as electron donor were identified as representatives of the alpha-3 subclass of the Proteobacteria (aerobic) and of the Natronolimnicola - Alkalispirillum group in the gammaproteobacteria (nitrate-reducing). While all chemolithotrophic isolates from soda lakes belong to the alkaliphiles with a pH optimum for growth around 10, only the sulfur-oxidizing group included species able to grow under hypersaline conditions. This indicates that carbon and nitrogen cycles in the hypersaline alkaline lakes might not be closed.

Fresh Water↗

PubMed2025

The Effect of Colesevelam on the Microbiome in Postoperative Crohn's Disease.

BACKGROUND: While surgery plays a pivotal role in the management of ileal Crohn's disease, the risk of endoscopic recurrence following an ileocaecal resection can be greater than 65% within 12 months of surgery. More than 90% of patients with Crohn's disease have a concomitant diagnosis of bile acid diarrhea following an ileal resection. This pilot study aimed to assess whether the use of bile acid sequestrants in patients with Crohn's disease who have undergone a primary terminal ileal resection with concomitant bile acid diarrhea can alter the microbiome and prevent disease recurrence. METHODS: Patients with Crohn's disease who underwent a primary terminal ileal resection and had symptoms of diarrhea within 1-3 months of surgery underwent 75SeHCAT testing for bile acid diarrhea. If positive (75SeHCAT ≤ 15%), patients were treated with colesevelam and stool samples were collected at 4 weeks, 8 weeks, and 6-12 months posttreatment. If negative (75SeHCAT > 15%), treatment was not given and were reviewed in the clinic as per local guidelines. All patients underwent a 6-12 month postoperative colonoscopy where further stool samples and mucosal biopsies were taken. Disease activity was established using the endoscopic Rutgeert's score, with disease remission defined as Rutgeert's score <i2 and disease recurrence ≥i2. 16S ribosomal RNA gene analysis was undertaken for the collected fecal and mucosal samples to assess α/β-diversity and microbial composition. RESULTS: A total of 14 patients who completed the study, 10 of whom had a 75SeHCAT positive diagnosis of bile acid diarrhea and were started on treatment with colesevelam. Four patients did not require treatment as 3 were asymptomatic and 1 had a negative 75SeHCAT scan. Three of the fourteen patients had disease recurrence at their 6-12 month postoperative colonoscopy assessment, of which 1 patient was taking colesevelam and 2 patients were not taking colesevelam. A total of 44 fecal samples and 44 mucosal biopsies underwent 16S ribosomal RNA gene analysis to assess α/β-diversity and microbial composition. In the colesevelam treated patients there was no significant difference in α/β-diversity pre- and posttreatment. Pretreatment, the 3 most abundant bacterial classes in all patients were Bacteroidia, Clostridia, and Gammaproteobacteria. Following 6-12 months of treatment, out of the 9 patients on colesevelam, 5/9 (55.6%) had a reduction in Bacteroidia, 9/9 (100%) had an increase in Clostridia, and 7/9 (77.8%) had a reduction in Gammaproteobacteria. Of the 2 patients not given colesevelam, one showed a reduction in Bacteroidia, increase in Clostridia and a reduction in Gammaproteobacteria. CONCLUSIONS: This small pilot study demonstrated that patients who were given colesevelam, were more likely to be in disease remission at their 6-12 months colonoscopy review compared with those not treated. Furthermore, treatment with colesevelam may have a role in altering the microbiome to help maintain remission states in postoperative Crohn's disease. Larger mechanistic studies are now needed to confirm these findings and demonstrate statistical significance as well as investigate whether this benefit may be present even in those patients with 75SeHCAT negative disease.

Humans↗

PubMed2005

Aquimonas voraii gen. nov., sp. nov., a novel gammaproteobacterium isolated from a warm spring of Assam, India.

A bacterial strain designated GPTSA 20(T), which was isolated from a warm spring in Assam, India, was characterized by using a polyphasic approach. The cells were Gram-negative, aerobic rods, which could not utilize or produce acid from most of the carbohydrates tested. The predominant fatty acids were C(15:0) iso (25.04%), C(17:1) iso omega9c (19.28%), C(16:0) iso (17.73%) and C(11:0) iso 3-OH (9.34%). The G+C content was 75 mol%. From 16S rRNA gene sequence analysis (1433 nucleotides, continuous stretch), it was confirmed that strain GPTSA 20(T) belonged to the class 'Gammaproteobacteria'. The closest 16S rRNA gene sequence similarity found (98.2%) was with an uncultured bacterium clone, NB-03 (accession no. AB117707), from an autotrophic nitrifying biofilm. Among culturable bacteria, the closest sequence similarities were with Fulvimonas soli (93.0%), Silanimonas lenta (92.8%), Thermomonas hydrothermalis (92.4%), Frateuria aurantia (91.9%), Rhodanobacter lindaniclasticus (91.9%), Thermomonas haemolytica (91.9%) and Pseudoxanthomonas taiwanensis (91.8%); similarities of less than 91.8% were obtained with other members of the class 'Gammaproteobacteria'. From the biochemical, physiological, chemotaxonomic and phylogenetic analysis, it was clear that strain GPTSA 20(T) was quite different from members of known genera of the class 'Gammaproteobacteria'. Therefore, it is proposed that strain GPTSA 20(T) represents a novel species within a new genus, with the name Aquimonas voraii gen. nov., sp. nov. The type strain is GPTSA 20(T) (=MTCC 6713(T)=JCM 12896(T)).

Bacterial Typing Techniques↗

PubMed2006

Degradation of low-ethoxylated nonylphenols by a Stenotrophomonas strain and development of new phylogenetic probes for Stenotrophomonas spp. detection.

An aerobic bacterium (BCc6), isolated from nonylphenol polyethoxylates (NPEOs)-contaminated sludge, was shown to be capable of degrading low-ethoxylated NPEO mixtures. Sequencing of 16S rRNA gene (rDNA) showed that it clustered with Stenotrophomonas nitritireducens. Fluorescent in situ hybridization (FISH), performed on BCc6 strain and on the previously isolated Stenotrophomonas BCaL2, also involved in NPEO degradation but clustering with S. maltophilia, showed that strain BCc6 did not hybridize with the S. maltophilia-specific probe, and neither of the two strains hybridized with probes targeted to the Gammaproteobacteria site, rDNA analyses performed on the two strains evidenced two new polymorphisms, the first one at the 23S rRNA Gammaproteobacteria site, characterizing the known members of the Stenotrophomonas genus, and the other one at the 16S rRNA level, characteristic of S. nitritireducens. Two new FISH probes were designed accordingly, tested on control bacterial cultures, and employed for in situ monitoring of Stenotrophomonas representatives.

Biodegradation, Environmental↗

PubMed2004

Gamma proteobacteria can nodulate legumes of the genus Hedysarum.

The bacteria hosted in the root nodules of the three Mediterranean wild legume species Hedysarum carnosum, Hedysarum spinosissimum subsp. capitatum, and Hedysarum pallidum, growing in native stands in different habitats in Algeria were isolated. Bacteria were recovered on yeast-mannitol-agar or on minimal media from a total of 52 nodules. Isolates were analyzed by Amplified Ribosomal DNA Restriction Analysis (ARDRA) using the enzyme CfoI, and further sorted by RAPD fingerprinting. A total of ten different types were found and their amplified 16S rDNA was sequenced and compared to databases. The BLAST alignment indicates that all the species whose sequences share 98 to 100% identity to the bacteria found in these nodules belong to the class Gammaproteobacteria and include Pantoea agglomerans, Enterobacter kobei, Enterobacter cloacae, Leclercia adecarboxylata, Escherichia vulneris, and Pseudomonas sp. No evidence of any rhizobial-like sequence was found even upon amplifying from the bulk of microbial cells obtained from the squashed nodules, suggesting that the exclusive occupants of the nodules formed by the three plants tested are members of the orders Enterobacteriales or Pseudomonadales. This is the first report of Gammaproteobacteria associated with legume nodules. Despite the presence of the related crop plant Hedysarum coronarium, specifically nodulated by Rhizobium sullae, these three Hedysarum species demonstrate to have undergone a separate path in terms of endophytic interactions with bacteria. An hypothesis to account for differences between the symbiotic relationships engaged by man-managed legumes, and those found in plants whose ecology is independent from human action, is discussed.

Algeria↗

PubMed2006

Dokdonella koreensis gen. nov., sp. nov., isolated from soil.

Two Gram-negative, motile, non-spore-forming and rod-shaped bacterial strains, DS-123T and DS-140, were isolated from soil and their taxonomic positions were investigated by a polyphasic study. Strains DS-123T and DS-140 grew optimally at 30 degrees C and pH 6.5 without NaCl. They contained Q-8 as the predominant ubiquione and iso-C(17 : 1)omega9c, iso-C(17 : 0) and iso-C(15 : 0) as the major fatty acids. Major polar lipids detected in the two strains were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and an amino-group-containing lipid that was ninhydrin-positive. Their DNA G+C contents were 71.0 mol%. Strains DS-123T and DS-140 exhibited no difference in their 16S rRNA gene sequences and possessed a mean DNA-DNA relatedness level of 92 %. Phylogenetic trees based on 16S rRNA gene sequences showed that strains DS-123T and DS-140 formed a distinct evolutionary lineage within the Gammaproteobacteria. The 16S rRNA gene sequences of strains DS-123T and DS-140 exhibited similarity values of less than 94.1 % to members of the Gammaproteobacteria. Strains DS-123T and DS-140 were distinguished from phylogenetically related genera by differences in some phenotypic properties. On the basis of phenotypic, phylogenetic and genetic data, it is proposed that strains DS-123T (= KCTC 12396T = DSM 17203T) and DS-140 be classified in a novel genus and species, Dokdonella koreensis gen. nov., sp. nov.

Base Composition↗

PubMed2006

Marinimicrobium koreense gen. nov., sp. nov. and Marinimicrobium agarilyticum sp. nov., novel moderately halotolerant bacteria isolated from tidal flat sediment in Korea.

Two moderately halotolerant Gram-negative bacteria were isolated from tidal flat sediment of the South Sea in Korea (the Korea Strait). The strains, designated M9T and M18T, were strictly aerobic, rod-shaped and non-spore-forming and motile with a flagellum and their major fatty acids were C(16:0) and C(19:0) cyclo omega8c. Strains M9T and M18T could grow in the presence of up to 13-15% (w/v) NaCl, but their optimum salt concentrations were relatively low (0-3%, w/v). The major predominant isoprenoid quinone was Q-8 and the G + C content of the genomic DNA was 57-58 mol%. Phylogenetic analyses and comparative 16S rRNA gene sequence studies revealed that strains M9T and M18T formed a phylogenetic lineage distinct from the genus Teredinibacter within the class Gammaproteobacteria and were most closely related to the genera Microbulbifer, Saccharophagus and Teredinibacter, with less than 92.5% 16S rRNA gene sequence similarity. The level of 16S rRNA gene sequence similarity between the two strains was 96.7%. On the basis of physiological and phylogenetic properties, strains M9T and M18T represent separate species within a novel genus of the class Gammaproteobacteria, for which the names Marinimicrobium koreense gen. nov., sp. nov. (type species) and Marinimicrobium agarilyticum sp. nov. are proposed. The type strains of Marinimicrobium koreense and Marinimicrobium agarilyticum are M9T (= KCTC 12356T = DSM 16974T) and M18T (= KCTC 12357T = DSM 16975T), respectively.

Base Composition↗

PubMed2006

Salicola marasensis gen. nov., sp. nov., an extremely halophilic bacterium isolated from the Maras solar salterns in Peru.

Six strains of extremely halophilic bacteria were isolated from several crystallizer ponds of the Maras solar salterns in the Peruvian Andes. On the basis of 16S rRNA gene sequence similarity, G+C contents and DNA-DNA hybridization results, the six isolates constituted a genomically homogeneous group affiliated with the Gammaproteobacteria. The closest relatives were members of the halophilic genera Halovibrio and Halospina, which showed 16S rRNA gene sequence similarities below 97 % and whole-genome hybridization levels below 33 % for the type strain, 7Sm5(T). From the genomic and phenotypic properties of the six novel isolates and phylogenetic reconstruction based on 16S rRNA gene sequence analysis, they can be considered to represent a novel genus within the Gammaproteobacteria. On the basis of the taxonomic study, a novel genus, Salicola gen. nov., is proposed containing the single species Salicola marasensis sp. nov., which is the type species. The type strain of Salicola marasensis is 7Sm5(T) (=CECT 7107(T)=CIP 108835(T)).

Bacterial Typing Techniques↗

PubMed2004

Reconstruction of the evolutionary history of the LexA-binding sequence.

In recent years, the recognition sequence of the SOS repressor LexA protein has been identified for several bacterial clades, such as the Gram-positive, green non-sulfur bacteria and Cyanobacteria phyla, or the 'Alphaproteobacteria', 'Deltaproteobacteria' and 'Gammaproteobacteria' classes. Nevertheless, the evolutionary relationship among these sequences and the proteins that recognize them has not been analysed. Fibrobacter succinogenes is an anaerobic Gram-negative bacterium that branched from a common bacterial ancestor immediately before the Proteobacteria phylum. Taking advantage of its intermediate position in the phylogenetic tree, and in an effort to reconstruct the evolutionary history of LexA-binding sequences, the F. succinogenes lexA gene has been isolated and its product purified to identify its DNA recognition motif through electrophoretic mobility assays and footprinting experiments. After comparing the available LexA DNA-binding sequences with the F. succinogenes one, reported here, directed mutagenesis of the F. succinogenes LexA-binding sequence and phylogenetic analyses of LexA proteins have revealed the existence of two independent evolutionary lanes for the LexA recognition motif that emerged from the Gram-positive box: one generating the Cyanobacteria and 'Alphaproteobacteria' LexA-binding sequences, and the other giving rise to the F. succinogenes and Myxococcus xanthus ones, in a transitional step towards the current 'Gammaproteobacteria' LexA box. The contrast between the results reported here and the phylogenetic data available in the literature suggests that, some time after its emergence as a distinct bacterial class, the 'Alphaproteobacteria' lost its vertically received lexA gene, but received later through lateral gene transfer a new lexA gene belonging to either a cyanobacterium or a bacterial species closely related to this phylum. This constitutes the first report based on experimental evidence of lateral gene transfer in the evolution of a gene governing such a complex regulatory network as the bacterial SOS system.

Alphaproteobacteria↗