Anoxybacillus karvacharensis sp. nov., a novel thermophilic bacterium isolated from the Karvachar geothermal spring in Nagorno-Karabakh

Twelve thermophilic Anoxybacillus strains were isolated from sediment and water samples from a Karvachar hot spring located in the northern part of Nagorno-Karabakh. Based on phenotypic, chemotaxonomic and phylogenetic characteristics, one of the isolates, designated strain K1^T, was studied in detail. The cells are straight, motile rods that are 0.2–0.4×2.3–7.2 µm in size. The strain is a Gram-stain-positive, moderately thermophilic facultative anaerobe with an optimum growth temperature of 60–65 °C and a growth temperature range of 45–70 °C. Growth of strain K1^T was observed at pH 6–11 (optimum, pH 8–9) and was inhibited in the presence of NaCl concentrations above 2.5 % (optimum, 1–1.5 %). The isolate could utilize a wide variety of carbon sources, including d-arabinose, d-ribose, d-galactose, d-fructose, d-mannitol, maltose, aesculin, melibiose, sucrose, trehalose, raffinose, amidone, glycogen, turanose, d-lyxose, d-tagatose, potassium gluconate and 2-keto-gluconate. The strain was able to hydrolyse starch, casein and gelatin, was positive for oxidase and catalase, and reduced nitrate to nitrite, but was negative for H₂S production. Production of urease and indole was not observed. The major cellular fatty acids were C_15 : 0 iso, C_16 : 0 and C_17 : 0 iso (52.5, 13.6 and 19.6 % of total fatty acids, respectively). Strain K1^T shares >99 % 16S rRNA sequence similarity and a genomic average nucleotide identity value of 94.5 % with its closest relative, Anoxybacillus flavithermus DSM 2641^T, suggesting that it represents a separate and novel species, for which the name Anoxybacillus karvacharensis sp. nov. is proposed. The type strain of Anoxybacillus karvacharensis is K1^T (=DSM 106524^T=KCTC 15807^T).

The extremophile Anoxybacillus sp. PC2 isolated from Brazilian semiarid region (Caatinga) produces a thermostable keratinase

The aim of this study was to select and identify thermophilic bacteria from Caatinga biome (Brazil) able to produce thermoactive keratinases and characterize the keratinase produced by the selected isolate. After enrichment in keratin culture media, an Anoxybacillus caldiproteolyticus PC2 was isolated. This thermotolerant isolate presents a remarkable feature producing a thermostable keratinase at 60°C. The partially purified keratinase, identified as a thermolysin-like peptidase, was active at a pH range of 5.0-10.0 with maximal activity at a temperature range of 50-80°C. The optimal activity was observed at pH 7.0 and 50-60°C. These characteristics are potentially useful for biotechnological purposes such as processing and bioconversion of keratin.

Introduction of novel thermostable α-amylases from genus Anoxybacillus and proposing to group the Bacillaceae related α-amylases under five individual GH13 subfamilies

Among the thermophilic Bacillaceae family members, α-amylase production of 15 bacilli from genus Anoxybacillus was investigated, some of which are biotechnologically important. These Anoxybacillus α-amylase genes displayed ≥ 91.0% sequence similarities to Anoxybacillus enzymes (ASKA, ADTA and GSX-BL), but relatively lower similarities to Geobacillus (≤ 69.4% to GTA, Gt-amyII), and Bacillus aquimaris (≤ 61.3% to BaqA) amylases, all formerly proposed only in a Glycoside Hydrolase 13 (GH13) subfamily. The phylogenetic analyses of 63 bacilli-originated protein sequences among 93 α-amylases revealed the overall relationships within Bacillaceae amylolytic enzymes. All bacilli α-amylases formed 5 clades different from 15 predefined GH13 subfamilies. Their phylogenetic findings, taxonomic relationships, temperature requirements, and comparisonal structural analyses (including their CSR-I-VII regions, 12 sugar- and 4 calcium-binding sites, presence or absence of the complete catalytic machinery, and their currently unassigned status in a valid GH13 subfamiliy) revealed that these five GH13 α-amylase clades related to familly share some common characteristics, but also display differentiative features from each other and the preclassified ones. Based on these findings, we proposed to divide Bacillaceae related GH13 subfamilies into 5 individual groups: the novel a2 subfamily clustered around α-amylase B2M1-A (Anoxybacillus sp.), the a1, a3 and a4 subfamilies (including the representatives E184aa-A (Anoxybacillus sp.), ATA (Anoxybacillus tepidamans), and BaqA,) all of which were composed from the division of the previously grouped single subfamily around α-amylase BaqA, and the undefinite subfamily formerly defined as xy including Bacillus megaterium NL3.

[Structure and function of a novel thermostable pullulanase]

Research on novel pullulanase has major significance on the domestic industrialization of pullulanase and the breakdown of foreign monopoly. A thermophilic bacteria LM 18-11 producing thermostable pullulanase was isolated from Lunma hot springs of Yunnan province. It was identified as Anoxybacillus sp. by 16S rDNA phylogenetic analysis. Full-length pullulanase gene was cloned from Anoxybacillus sp. LM18-11. The optimum temperature of the pullulanase was between 55 and 60 degrees C with a half-life as long as 48 h at 60 degrees C; and its optimum pH was between 5.6 and 6.4. V(max) and K(m) of the pullulanase was measured as 750 U/mg and 1.47 mg/mL, which is the highest specific activity reported so far. The pullulanase crystals structure showed a typical alpha-amylase family structure. The N-terminal has a special substrate binding domain. Activity and substrate binding were decreased when the domain was deleted, the V(max) and K(m) were 324 U/mg and 1.95 mg/mL, respectively. The pullulanase was highly heterologous expressed in Bacillus subtilis by P43 promoter. The extracellular enzyme activity was 42 U/mL, which increased more than 40 times compared to the initial strain. This pullulanase has good application prospects.

Anoxybacillus calidus sp. nov., a thermophilic bacterium isolated from soil near a thermal power plant

A novel thermophilic, Gram-stain-positive, facultatively anaerobic, endospore-forming, motile, rod-shaped bacterium, strain C161ab(T), was isolated from a soil sample collected near Kizildere, Saraykoy-Buharkent power plant in Denizli. The isolate could grow at temperatures between 35 and 70 °C (optimum 55 °C), at pH 6.5-9.0 (optimum pH 8.0-8.5) and with 0-2.5 % NaCl (optimum 0.5 %, w/v). The strain formed cream-coloured, circular colonies and tolerated up to 70 mM boron. Its DNA G+C content was 37.8 mol%. The peptidoglycan contained meso-diaminopimelic acid as the diagnostic diamino acid. Strain C161ab(T) contained menaquinones MK-7 (96 %) and MK-6 (4 %). The major cellular fatty acids were iso-branched fatty acids: iso-C15 : 0 (52.2 %) and iso-C17 : 0 (28.0 %,) with small amounts of C16 : 0 (7.4 %). Phylogenetic analysis based on the 16S rRNA gene revealed 94.6-96.8 % sequence similarity with all recognized species of the genus Anoxybacillus. Strain C161ab(T) showed the greatest sequence similarity to Anoxybacillus rupiensis DSM 17127(T) and Anoxybacillus voinovskiensis DSM 17075(T), both had 96.8 % similarity to strain C161ab(T), as well as to Anoxybacillus caldiproteolyticus DSM 15730(T) (96.6 %). DNA-DNA hybridization revealed low levels of relatedness with the closest relatives of strain C161ab(T), A. rupiensis (21.2 %) and A. voinovskiensis (16.5 %). On the basis of the results obtained from phenotypic, chemotaxonomic, genomic fingerprinting, phylogenetic and hybridization analyses, the isolate is proposed to represent a novel species, Anoxybacillus calidus sp. nov. (type strain C161ab(T) = DSM 25520(T) = NCIMB 14851(T)).

Recent discoveries and applications of Anoxybacillus

The Bacillaceae family members are a good source of bacteria for bioprocessing and biotransformation involving whole cells or enzymes. In contrast to Bacillus and Geobacillus, Anoxybacillus is a relatively new genus that was proposed in the year 2000. Because these bacteria are alkali-tolerant thermophiles, they are suitable for many industrial applications. More than a decade after the first report of Anoxybacillus, knowledge accumulated from fundamental and applied studies suggests that this genus can serve as a good alternative in many applications related to starch and lignocellulosic biomasses, environmental waste treatment, enzyme technology, and possibly bioenergy production. This current review provides the first summary of past and recent discoveries regarding the isolation of Anoxybacillus, its medium requirements, its proteins that have been characterized and cloned, bioremediation applications, metabolic studies, and genomic analysis. Comparisons to some other members of Bacillaceae and possible future applications of Anoxybacillus are also discussed.

Taxonomic classification of Anoxybacillus isolates from geothermal regions in Turkey by 16S rRNA gene sequences and ARDRA, ITS-PCR, Rep-PCR analyses

A total of 115 endospore-forming bacilli were taken for 16S rRNA gene sequence analyses and clustered among 7 genera. In this paper, the most abundant thermophiles belonging to genus Anoxybacillus with its 53 isolates are presented. The Anoxybacillus species, some of which were producing biotechnologically valuable enzymes, mostly displayed amylolytic and glucosidic activities and the ability of carbohydrate degradation made them superior in number among the other bacilli in these extreme habitats. In comparative sequence analyses, similarities ranged from 91.1% to 99.9% between the isolates and the type strains. Isolates were clustered into eight phylogenetic lineages within the type strains of A. kamchatkensis, A. flavithermus, A. kamchatchensis subsp. asaccharedens, and A. salavatliensis. In addition, C161ab and A321 were proposed as novel species which displayed < 97.0% similarities to their closest relatives. Moreover, their individual AluI, HaeIII, and TaqI ARDRA restriction patterns, ITS-, (GTG)5-, and BOX-PCR fingerprintings generated 27, 28, 31, 35, 40, and 41 clusters, respectively. The twelve type strains and 35 of the isolates showed unique distinctive patterns from all the others at least in two of these analyses. These phenotypic and genomic characters allowed us to differentiate their genotypic diversity from the reference strains.

Decolorization of dye Reactive Black 5 by newly isolated thermophilic microorganisms from geothermal sites in Galicia (Spain)

In this study, thermophilic microbial strains from thermal spots in northwestern Spain displaying excellent decolorization capability were isolated. The research work tackled: (i) the ability of consortia to degrade a model di-azo dye Reactive Black at different pHs in flask cultures, obtaining that just neutral pHs licensed degradation levels near to 70%, (ii) the isolation of tree of the bacteria, which rendered possible reaching high levels of decolorization (80%) after just 24 h in aerobic conditions, and which were identified through 16S rRNA sequencing to possess high homology (99%) with Anoxybacillus pushchinoensis, Anoxybacillus kamchatkensis and Anoxybacillus flavithermus, and (iii) the cultivation of the isolates in a bench-scale bioreactor, which led to a decolorization rate two-fold higher than that obtained in flask cultures. Therefore, this work makes up the first time that a decolorization process of an azo dye by thermophilic microorganisms in aerobic conditions is investigated.

Anoxybacillus mongoliensis sp. nov., a novel thermophilic proteinase producing bacterium isolated from alkaline hot spring, central Mongolia

A Gram reaction positive, spore-forming, facultative anaerobic bacterium belonging to the Phylum Firmicutes, was isolated from alkaline hot (80 degrees C, pH 9.8 spring Tsenher, central Mongolia. The cells were rod shaped, feebly motile, peritrichously flagellated. Strain T4 was moderately thermophilic with optimum growth at 60 degrees C. Maximum temperature for growth was between 70 and 75 degrees C; minimum temperature for growth was between 35 and 30 degrees C. Alkalitolerant, optimum pH for growth was 8.0; minimum pH for growth was between 5.0 and 5.5 and maximum was between 10.5 and 10.8. The growth was observed at NaCl concentrations of 0-5% (w/v) with the optimum at 0.2-0.5%. No growth was observed at 6% NaCl (w/v). Aerobically, the strain utilized proteinaceous substrates, organic acids and a range of carbohydrates including glucose, ribose, sucrose and xylose as well. Anaerobically, only glucose and sucrose were utilized. Strain T4T produced thermostable alkaline subtilisin-like serine proteinase. The G + C content was 44.2 mol. % (td). On the basis of 16S rRNA gene sequence similarity strain T4(T) was shown to be closely related to the members of the genus Anoxybacillus (family Bacillaceae, class "Bacilli"). DNA-DNA hybridization data revealed that strain T4T had only 38% relatedness to A. flavithermus and 28% relatedness to A. pushchinoensis. Based on its morphology, physiology, phylogenetic relationship and its low DNA-DNA relatedness values with validly published species of Anoxybacillus, it is proposed that strain T4T represents a novel species Anoxybacillus mongoliensis sp. nov., with the type strain T4(T) (=DSM 19169 = VKM 2407).