Wajdi Ben Hania

Defluviitoga tunisiensis gen. nov., sp. nov., a thermophilic bacterium isolated from a mesothermic and anaerobic whey digester

Strain SulfLac1(T), a thermophilic, anaerobic and slightly halophilic, rod-shaped bacterium with a sheath-like outer structure (toga), was isolated from a whey digester in Tunisia. The strains non-motile cells measured 3-30×1 µm and appeared singly, in pairs or as long chains. The novel strain reduced thiosulfate and elemental sulfur, but not sulfate or sulfite, into sulfide. It grew at 37-65 °C (optimum 55 °C), at pH 6.5-7.9 (optimum pH 6.9) and with 0.2-3 % (w/v) NaCl (optimum 0.5 %). The G+C content of the strains genomic DNA was 33.6 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain SulfLac1(T) was most closely related to Petrotoga mobilis (91.4 % sequence similarity). Based on phenotypic, phylogenetic and chemotaxonomic evidence, strain SulfLac1(T) represents a novel species of a new genus within the order Thermotogales, for which the name Defluviitoga tunisiensis gen. nov., sp. nov. is proposed. The type strain of the type species is SulfLac1(T) ( = DSM 23805(T) = JCM 17210(T)).

Aminobacterium thunnarium sp. nov., a mesophilic, amino acid-degrading bacterium isolated from an anaerobic sludge digester, pertaining to the phylum Synergistetes.

A new Gram-staining-positive, non-sporulating, mesophilic, amino acid-degrading anaerobic bacterium, designated strain OTA 102(T), was isolated from an anaerobic sequencing batch reactor treating wastewater from cooking tuna. The cells were curved rods (0.6-2.5×0.5 µm) and occurred singly or in pairs. The strain was motile by means of one lateral flagellum. Strain OTA 102(T) grew at temperatures between 30 and 45 °C (optimum 40 °C), between pH 6.0 and 8.4 (optimum pH 7.2) and NaCl concentrations between 1 and 5 % (optimum 2 %, w/v). Strain OTA 102(T) required yeast extract for growth. Serine, threonine, glycine, cysteine, citrate, fumarate, α-ketoglutarate and pyruvate were fermented. When co-cultured with Methanobacterium formicicum as the hydrogen scavenger, strain OTA 102(T) oxidized alanine, valine, leucine, isoleucine, aspartate, tyrosine, methionine, histidine and asparagine. The genomic DNA G+C content of strain OTA 102(T) was 41.7 mol%. The main fatty acid was iso-C15 : 0. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain OTA 102(T) was related to Aminobacterium colombiense and Aminobacterium mobile (95.5 and 95.2 % similarity, respectively), of the phylum Synergistetes. On the basis of phylogenetic, genetic and physiological characteristics, strain OTA 102(T) is proposed to represent a novel species of the genus Aminobacterium, Aminobacterium thunnarium sp. nov. The type strain is OTA 102(T) ( = DSM 27500(T) = JCM 19320(T)).

Characterization of the first cultured representative of a Bacteroidetes clade specialized on the scavenging of cyanobacteria

The anaerobic, mesophilic and moderately halophilic strain L21-Spi-D4T was recently isolated from the suboxic zone of a hypersaline cyanobacterial mat using protein-rich extracts of Arthrospira (formerly Spirulina) platensis as substrate. Phylogenetic analyses based on 16S rRNA genes indicated an affiliation of the novel strain with the Bacteroidetes clade MgMjR-022, which is widely distributed and abundant in hypersaline microbial mats and heretofore comprised only sequences of uncultured bacteria. Analyses of the complete genome sequence of strain L21-Spi-D4T revealed a possible specialization on the degradation of cyanobacterial biomass. Besides genes for enzymes degrading specific cyanobacterial proteins a conspicuous transport complex for the polypeptide cyanophycin could be identified that is homologous to typical polysaccharide utilization loci of Bacteroidetes. A distinct and reproducible co-occurrence pattern of environmental 16S rRNA gene sequences of the MgMjR-022 clade and cyanobacteria in the suboxic zone of hypersaline mats points to a specific dependence of members of this clade on decaying cyanobacteria. Based on a comparative analysis of phenotypic, genomic and ecological characteristics we propose to establish the novel taxa Salinivirga cyanobacteriivorans gen. nov., sp. nov., represented by the type strain L21-Spi-D4T , and Salinivirgaceae fam. nov., comprising sequences of the MgMjR-022 clade.

Reclassification of Anaerobaculum mobile, Anaerobaculum thermoterrenum, Anaerobaculum hydrogeniformans as Acetomicrobium mobile comb. nov., Acetomicrobium thermoterrenum comb. nov. and Acetomicrobium hydrogeniformans comb. nov., respectively, and emendation of the genus Acetomicrobium

Taking into account their 16S rRNA gene sequences, it appears that Acetomicrobium flavidum and the three species of the genus Anaerobaculum described so far belong to the same phylogenetic clade with high levels (>95 %) of similarity. In this respect, these three Anaerobaculum species should be reclassified within the genus Acetomicrobium, which has priority over the genus Anaerobaculum, which was validated since the genus Acetomicrobium. The DNA G+C content of Acetomicrobium flavidum is 47.1 mol%, which is of the same order as that of the three Anaerobaculum species. All these bacteria have in common iso-C15 : 0 as their main fatty acid. Based on further phylogenetic, genetic and chemotaxonomic studies, we propose that Anaerobaculum mobile ( = DSM 13181T = JCM 12221T), Anaerobaculum thermoterrenum ( = DSM 13490T = ACM 5076T) and Anaerobaculum hydrogeniformans ( = DSM 22491T = ATCC BAA-1850T) be reclassified as Acetomicrobium mobile comb. nov., Acetomicrobium thermoterrenum comb. nov. and Acetomicrobium hydrogeniformans comb. nov., respectively. The four bacterial species belong to the phylum Synergistetes.

Draft genome sequence of Mesotoga strain PhosAC3, a mesophilic member of the bacterial order Thermotogales, isolated from a digestor treating phosphogypsum in Tunisia

Mesotoga strain PhosAc3 was the first mesophilic cultivated member of the order Thermotogales. This genus currently contain two described species, M. prima and M. infera. Strain PhosAc3, isolated from a Tunisian digestor treating phosphogypsum, is phylogenetically closely related to M. prima strain MesG1.Ag.4.2T. Strain PhosAc3 has a genome of 3.1 Mb with a G+C content of 45.2%. It contains 3,051 protein-coding genes of which 74.6% have their best reciprocal BLAST hit in the genome of the type species, strain MesG1.Ag.4.2T. For this reason we propose to assign strain PhosAc3 as a novel ecotype of the Mesotoga prima species. However, in contrast with the M. prima type strain, (i) it does not ferment sugars but uses them only in the presence of elemental sulfur as terminal electron acceptor, (ii) it produces only acetate and CO2 from sugars, whereas strain MesG1.Ag.4.2T produces acetate, butyrate, isobutyrate, isovalerate, 2-methyl-butyrate and (iii) sulfides are also end products of the elemental sulfur reduction in theses growth conditions.

Balneicella halophila gen. nov., sp. nov., an anaerobic bacterium, isolated from a thermal spring and description of Balneicellaceae fam. nov.

A mesophilic anaerobic bacterium, designated KHALHBd91T was isolated from the moderately hot spring of Hammam Biadha, Tunisia. The strain was Gram-staining-negative, non-sporulating, non-motile and rod-shaped, appearing singly (0.5-2.0×0.5-1 µm). It grew anaerobically at temperatures between 20 and 50 °C (optimum 37 °C) and at pH values between 5.5 and 7.8 (optimum 7.0). It required NaCl for growth, with growth observed at up 8.5 % and an optimum at 2.5 %. KHALHBd91T used glucose, galactose, maltose, pyruvate, lactate, fumarate and yeast extract as electron donors. The end-products from glucose fermentation were acetate, propionate, succinate and CO2. Nitrate, nitrite, thiosulfate, elemental sulfur, sulfate and sulfite were not used as terminal electron acceptors. The predominant cellular fatty acids were anteiso-C15 : 0 and iso-C15 : 0. The respiratory quinone was MK-6. The main polar lipids consisted of lipids, phospholipids, glycolipids, aminolipids, phosphoaminoglycolipids and phosphatidylethanolamine. The DNA G+C content was 35.0 mol%. Phylogenetic analysis of the small-subunit ribosomal 16S rRNA gene sequence indicated that KHALHBd91T had Marinifilum fragile and Marinifilum flexuosum (phylum Bacteroidetes, class Bacteroidia, order Bacteroidales) as its closest relatives (similarity of 86.7 and 87.8 % respectively). The phylogenetic and physiological data fro the present study strongly indicate that the isolate represents a novel genus and species of a novel family, Balneicella halophila gen. nov., sp. nov., in the family Balneicellaceaefam. nov. The type strain is KHALHBd91T (=DSM28579T=JCM19909T).

Deciphering the adaptation strategies of Desulfovibrio piezophilus to hydrostatic pressure through metabolic and transcriptional analyses.

Desulfovibrio piezophilus strain C1TLV30(T) is a mesophilic piezophilic sulfate-reducer isolated from Wood Falls at 1700 m depth in the Mediterranean Sea. In this study, we analysed the effect of the hydrostatic pressure on this deep-sea living bacterium at the physiologic and transcriptomic levels. Our results showed that lactate oxidation and energy metabolism were affected by the hydrostatic pressure. Especially, acetyl-CoA oxidation pathway and energy conservation through hydrogen and formate recycling would be more important when the hydrostatic pressure is above (26 MPa) than below (0.1 MPa) the optimal one (10 MPa). This work underlines also the role of the amino acid glutamate as a piezolyte for the Desulfovibrio genus. The transcriptomic analysis revealed 146 differentially expressed genes emphasizing energy production and conversion, amino acid transport and metabolism and cell motility and signal transduction mechanisms as hydrostatic pressure responding processes. This dataset allowed us to identify a sequence motif upstream of a subset of differentially expressed genes as putative pressure-dependent regulatory element.

Melghiribacillus thermohalophilus gen. nov., sp. nov., a novel filamentous, endospore-forming, thermophilic and halophilic bacterium

A novel filamentous, endospore-forming, thermophilic and moderately halophilic bacterium designated strain Nari2A(T) was isolated from soil collected from an Algerian salt lake, Chott Melghir. The novel isolate was Gram-staining-positive, aerobic, catalase-negative and oxidase-positive. Optimum growth occurred at 50-55 °C, 7-10% (w/v) NaCl and pH 7-8. The strain exhibited 95.4, 95.4 and 95.2% 16S rRNA gene sequence similarity to Thalassobacillus devorans G19.1(T), Sediminibacillus halophilus EN8d(T) and Virgibacillus kekensis YIM-kkny16(T), respectively. The major menaquinone was MK-7. The polar lipid profile consisted of phosphatidylglycerol, diphosphatidylglycerol, three unknown phosphoglycolipids and two unknown phospholipids. The predominant cellular fatty acids were iso-C(15 : 0) and iso-C(17 : 0). The DNA G+C content was 41.9 mol%. Based on the phenotypic, chemotaxonomic and phylogenetic data, strain Nari2A(T) is considered to represent a novel species of a new genus in the family Bacillaceae , order Bacillales , for which the name Melghiribacillus thermohalophilus gen. nov., sp. nov. is proposed. The type strain of Melghiribacillus thermohalophilus is Nari2A(T) ( = DSM 25894(T) = CCUG 62543(T)).

Caldisalinibacter kiritimatiensis gen. nov., sp. nov., a Moderately Thermohalophilic Thiosulfate-Reducing Bacterium from a Hypersaline Microbial Mat

A novel anaerobic bacterium, designated L21-TH-D2T was isolated from the anoxic zone of a microbial mat of the hypersaline Lake 21 on the Kiritimati Atoll (Republic of Kiribati, Central Pacific). Cells were Gram-positive, spore-forming and motile slender rods. The novel strain grew anaerobically by fermentation at temperatures between 40 and 65°C (optimum 50–55°C) and at pH between 5–9 (optimum 6.9–7.0). It required at least 20 g L−1 NaCl for growth and tolerated up to 150 g L−1 NaCl (optimum at 50 g L−1). In the presence of yeast extract or peptone the novel strain fermented glucose, fructose, maltose, mannose and pyruvate. The end-products from glucose fermentation were acetate, ethanol, CO2 and H2. Nitrate, nitrite, elemental sulfur, sulfate, and sulfite were not used as electron acceptors, while thiosulfate was reduced to sulfide. The cellular fatty acids pattern was dominated by iso-C15:0 and iso-C15:0 DMA. The major polar lipids were identified as phosphatidylglycerol, phosphatidylethanolamine, an unidentified phospholipid and two different unidentified glycolipids. No respiratory lipoquinones or cytochromes were detected. The DNA G + C content was 30.7 mol%. The determined draft genome sequence of strain L21-TH-D2T revealed a specialization on a saccharolytic fermentative metabolism. Besides enzymes for substrate-level phosphorylation, several membrane-bound enzyme complexes, like an ion-translocating RNF complex and an F-type ATP synthase, were annotated in the genome sequence and seem to be involved in the energy metabolism. Phylogenetic analyses based on a comparison of 16S rRNA gene sequences placed the novel isolate in a clade of anaerobic halophilic or thermohalophilic bacteria within the clostridial subcluster XII. Significant phenotypic and phylogenetic differences prevent inclusion of the novel isolate in existing genera within the family Clostridiaceae, so that the novel taxon Caldisalinibacter kiritimatiensis gen. nov., sp. nov., is proposed. The type strain is L21-TH-D2T (= DSM 26826T = JCM 18664T).

Characterization of Desulfovibrio biadhensis sp. nov., isolated from a thermal spring.

A novel anaerobic, mesophilic, slightly halophilic sulfate-reducing bacterium, designated strain Khaled BD4(T), was isolated from waters of a Tunisian thermal spring. Cells were vibrio-shaped or sigmoids (5-7×1-1.5 µm) and occurred singly or in pairs. Strain Khaled BD4(T) was Gram-stain-negative, motile and non-sporulated. It grew at 25-45 °C (optimum 37 °C), at pH 5.5-8.3 (optimum pH 7.0) and with 0.5-8% NaCl (optimum 3%). It required vitamins or yeast extract for growth. Sulfate, thiosulfate, sulfite and elemental sulfur served as terminal electron acceptors, but not fumarate, nitrate or nitrite. Strain Khaled BD4(T) utilized H2 in the presence of 2 mM acetate (carbon source), but also lactate, formate, pyruvate and fumarate in the presence of sulfate. Lactate was incompletely oxidized to acetate. Amongst substrates used, only pyruvate was fermented. Desulfoviridin and c-type cytochrome were present. The G+C content of the DNA was 54.6 mol%. The main fatty acids were anteiso -C(15 : 0), iso-C(18 : 0), iso-C(17 : 0) and iso-C(14 : 0). Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain Khaled BD4(T) had Desulfovibrio giganteus DSM 4123(T) (96.7% similarity) as its closest phylogenetic relative. On the basis of 16S rRNA gene sequence comparisons together with genetic and physiological characteristics, strain Khaled BD4(T) is assigned to a novel bacterial species, for which the name Desulfovibrio biadhensis sp. nov. is proposed. The type strain is Khaled BD4(T) ( = DSM 28904(T) = JCM 30146(T)).