Improved biohydrogen production by co-fermentation of corn straw and excess sludge: Insights into biochemical process, microbial community and metabolic genes

The global climate change mainly caused by fossil fuels combustion promotes that zero-carbon hydrogen production through eco-friendly methods has attracted attention in recent years. This investigation explored the biohydrogen production by co-fermentation of corn straw (CS) and excess sludge (ES), as well as comprehensively analyzed the internal mechanism. The results showed that the optimal ratio of CS to ES was 9:1 (TS) with the biohydrogen yield of 101.8 mL/g VS, which was higher than that from the mono-fermentation of CS by 1.0-fold. The pattern of volatile fatty acids (VFAs) indicated that the acetate was the most preponderant by-product in all fermentation systems during the biohydrogen production process, and its yield was improved by adding appropriate dosage of ES. In addition, the content of soluble COD (SCOD) was reduced as increasing ES, while concentration of NH4+-N showed an opposite tendency. Microbial community analysis revealed that the microbial composition in different samples showed a significant divergence. Trichococcus was the most dominant bacterial genus in the optimal ratio of 9:1 (CS/ES) fermentation system and its abundance was as high as 41.8%. The functional genes prediction found that the dominant metabolic genes and hydrogen-producing related genes had not been significantly increased in co-fermentation system (CS/ES = 9:1) compared to that in the mono-fermentation of CS, implying that enhancement of biohydrogen production by adding ES mainly relied on balancing nutrients and adjusting microbial community in this study. Further redundancy analysis (RDA) confirmed that biohydrogen yield was closely correlated with the enrichment of Trichococcus.

Chryseobacterium gotjawalense sp. nov. Isolated from Soil in the Volcanic Forest Gotjawal, Jeju Island

Strain wdc7T, a rod-shaped bacterium, was isolated from soil in the Gotjawal Forest on Jeju Island, South Korea. Strain wdc7T was Gram stain-negative, facultatively anaerobic, catalase- and oxidase positive, yellow pigmented, and non-flagellated. It grew at 4-37 °C and pH 5.0-8.0 in 0-3% (w/v) NaCl. 16S rRNA gene sequencing analysis revealed that strain wdc7T belonged to the genus Chryseobacterium and was most closely related to Chryseobacterium salivictor NBC 122T, with a sequence similarity of 98.51%. Menaquinone 6 was the sole respiratory quinone, and C15:0 anteiso, C15:0 iso, and summed feature 9 were the major fatty acids. The genome length was 3.30 Mbp, with a 37% G + C content. Average amino acid identity, average nucleotide identity, and digital DNA-DNA relatedness between strain wdc7T and C. salivictor NBC 122T were 93.52%, 92.80%, and 49.7%, respectively. Digital genomic and polyphasic analyses showed that strain wdc7T likely represented a new species of the genus Chryseobacterium. We proposed the name Chryseobacterium gotjawalense sp. nov., with wdc7T (= KCTC 92440T = JCM 35602T) as the type strain.

Formulation of biogenic fluorescent pigmented PHB nanoparticles from Rhodanobacter sp. for drug delivery

Biogenic nanoparticles (NPs) have emerged as promising therapeutic formulations in effective drug delivery. Despite of various positive attributes, these NPs are often conjugated with various cytotoxic organic fluorophores for bioimaging, thereby reducing its effectiveness as a potential carrier. Herein, we aim to formulate biogenic fluorescent pigmented polyhydroxybutyrate (PHB) NPs from Rhodanobacter sp. strain KT31 (OK001852) for drug delivery. The bacterial strain produced 0.5 g L-1 of polyhydroxyalkanoates (PHAs) from 2.04 g L-1 of dry cell weight (DCW) under optimised conditions via submerged fermentation. Further, structural, thermal, and morphological charactersiation of the extracted PHAs was conducted using advance analytical technologies. IR spectra at 1719.25 cm-1 confirmed presence of C = O functional group PHB. NMR and XRD analysis validated the chemical structure and crystallinity of PHB. TG-DTA revealed Tm (168 °C), Td (292 °C), and Xc (35%) of the PHB. FE-SEM imaging indicated rough surface of the PHB film and the biodegradability was confirmed from open windro composting. WST1 assay showed no significant cell death (> 50%) from 100 to 500 µg/mL, endorsing non-cytotoxic nature of PHB. PHB NPs were uniform, smooth and spherical with size distribution and mean zeta potential 44.73 nm and 0.5 mV. IR and XRD peaks obtained at 1721.75 cm-1 and 48.42 Å denoted C = O and crystalline nature of PHB. Cell proliferation rate of PHB NPs was quite significant at 50 µg/mL, establishing the non-cytotoxic nature of NPs. Further, in vitro efficacy of the PHB NPs needs to be evaluated prior to the biomedical applications.

Glycerol amendment enhances biosulfidogenesis in acid mine drainage-affected areas: An incubation column experiment

Microbial sulfate (SO₄²⁻) reduction in Acid Mine Drainage (AMD) environments can ameliorate the acidity and extreme metal concentrations by consumption of protons via the reduction of SO₄²⁻ to hydrogen sulfide (H₂S) and the concomitant precipitation of metals as metal sulfides. The activity of sulfate-reducing bacteria can be stimulated by the amendment of suitable organic carbon sources in these generally oligotrophic environments. Here, we used incubation columns (IC) as model systems to investigate the effect of glycerol amendment on the microbial community composition and its effect on the geochemistry of sediment and waters in AMD environments. The ICs were built with natural water and sediments from four distinct AMD-affected sites with different nutrient regimes: the oligotrophic Filón Centro and Guadiana acidic pit lakes, the Tintillo river (Huelva, Spain) and the eutrophic Brunita pit lake (Murcia, Spain). Physicochemical parameters were monitored during 18 months, and the microbial community composition was determined at the end of incubation through 16S rRNA gene amplicon sequencing. SEM-EDX analysis of sediments and suspended particulate matter was performed to investigate the microbially-induced mineral (neo)formation. Glycerol amendment strongly triggered biosulfidogenesis in all ICs, with pH increase and metal sulfide formation, but the effect was much more pronounced in the ICs from oligotrophic systems. Analysis of the microbial community composition at the end of the incubations showed that the SRB Desulfosporosinus was among the dominant taxa observed in all sulfidogenic columns, whereas the SRB Desulfurispora, Desulfovibrio and Acididesulfobacillus appeared to be more site-specific. Formation of Fe³⁺ and Al³⁺ (oxy)hydroxysulfates was observed during the initial phase of incubation together with increasing pH while formation of metal sulfides (predominantly, Zn, Fe and Cu sulfides) was observed after 1–5 months of incubation. Chemical analysis of the aqueous phase at the end of incubation showed almost complete removal of dissolved metals (Cu, Zn, Cd) in the amended ICs, while Fe and SO₄²⁻ increased towards the water-sediment interface, likely as a result of the reductive dissolution of Fe(III) minerals enhanced by Fe-reducing bacteria. The combined geochemical and microbiological analyses further establish the link between biosulfidogenesis and natural attenuation through metal sulfide formation and proton consumption.

Te(IV) bioreduction in the sulfur autotrophic reactor: Performance, kinetics and synergistic mechanism

A laboratory-scale sulfur autotrophic reactor (SAR) was first constructed for treating tellurite [Te(IV)] wastewater. The SAR had excellent Te(IV) bioreduction efficiency (90-96%) at 5-30 mg/L and conformed to the First-order kinetic model. The Te(IV) bioreduction was elaborated deeply from extracellular polymeric substances (EPS) functions, microbial metabolic activity, key enzyme activity, microbial community succession and quorum sensing. Te(IV) stimulated the increase of redox substances in EPS and the improved cell membrane permeability led to the increase of electron transport system activity. Catalase and reduced nicotinamide adenine dinucleotide (NADH) alleviated the oxidative stress caused by Te(IV) toxicity to maintain metabolic activity. The increase of sulfur dioxygenase activity (SDO) suggested that more ATP produced by sulfur oxidation might provide energy for various physiological activities. Meanwhile, nitrate reductase (NAR), nitrite reductase (NIR) and sulfide: quinone oxidoreductase (SQR) played an active role in sulfur oxidation and Te(IV) bioreduction. Combined with the above results and dynamic succession of three functional microbial communities, a synergistic mechanism was proposed to explain the excellent performance of SAR. This work provided a promising strategy for Te(IV) wastewater treatment process and Te(IV) bioreduction mechanism.

Salinimonas marina sp. nov. Isolated from Jeju Island Marine Sediment

A Gram-stain-negative, rod-shaped, and strictly aerobic bacterium designated strain G2-b^T was isolated from the marine sediment around Jeju Island, South Korea. Strain G2-b^T was found to be catalase- and oxidase-positive, white-pigmented, motile with polar flagellum, and to grow optimally at 25 °C, pH 7.0 in the presence of 4% (w/v) NaCl. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain G2-b^T belongs to the genus Salinimonas and was closely related Salinimonas sediminis N102^T (96.7% sequence similarity), Salinimonas iocasae KX18D6^T (95.4%), Salinimonas lutimaris DPSR-4^T (94.7%), and Salinimonas chungwhensis BH030046^T (94.6%). Strain G2-b^T possessed ubiquinone 8 as the sole respiratory quinone, summed feature 3 and summed feature 8 as the major fatty acids, and phosphatidylethanolamine and phosphatidylglycerol as the major polar lipids. The genome size and G + C content of the strain G2-b^T were determined to be 3,765,169 bp, and 49.7%, respectively, as a complete circular genome. Based on the genomic analyses (e.g., average nucleotide identity and digital DNA-DNA hybridization), the strain G2-B^T likely represents a new species in the genus Salinimonas, for which we propose to name this novel bacterium Salinimonas marina sp. nov., and the type strain is designated G2-B^T (= KCTC 72817^T = VTCC 910110^T).

Draconibacterium halophilum sp. nov., A Halophilic Bacterium Isolated from Marine Sediment

A Gram-stain-negative, long-rod shaped, and facultatively anaerobic bacterium, designated as strain M1^T, was isolated from the marine sediment of Jeju Island, South Korea. Strain M1^T was found to be catalase- and oxidase-positive, light yellow-pigmented, non-motile, and non-flagellated, growing optimally at 30 °C, pH 7.0, and in the presence of 3% (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain M1^T belongs to the genus Draconibacterium and is closely related to Draconibacterium orientale FH5^T (97.2%), Draconibacterium sediminis JN14CK-3 ^T (96.5%), "Draconibacterium filum" F2^T (96.5%) and Draconibacterium mangrovi GM2-18 ^T (96.3% sequence similarity). The values for digital DNA-DNA hybridization ranged from 37.6 to 38.3% against D. orientale FH5^T, D. sediminis KN14CK-3 ^T, and D. mangrovi GM2-18 ^T, clearly indicating that strain M1^T represents a distinct species of the genus Draconibacterium. Strain M1^T has a 40.0% G + C content estimated by genome sequence, menaquinone 7 as the sole respiratory quinone, C_15:0 anteiso and C_15:0 iso as the major fatty acids, and phosphatidylethanolamine, an unidentified phospholipid, and unidentified lipids as the polar lipids. Based on the polyphasic characteristics, it is suggested that strain M1^T be assigned to the genus Draconibacterium as the type strain of a novel species, for which the name Draconibacterium halophilum sp. nov. is proposed. The type strain is M1^T (= KCTC 72809 ^T = VTCC 910107 ^T).

Kineobactrum salinum sp. nov., isolated from marine sediment

Strain M2^T, isolated from marine sediment collected at Jeju Island, was an aerobic, Gram-stain-negative, oxidase- and catalase-positive, motile, rod-shaped bacterium that formed circular, raised, yellow colonies. Strain M2^T grew at 15-42 °C, pH 5.5-9.0 and with 1-9 % (w/v) NaCl. Phylogenetic analysis based on its 16S rRNA gene sequences indicated that strain M2^T was closely related to Kineobactrum sediminis F02^T (98.0 % sequence similarity). Ubiquinone-8 was determined to be the sole respiratory quinone. Summed feature 3 (C_16 : 1  ω6c/C_16 : 1  ω7c) and summed feature 8 (C_18 : 1  ω7c/C_18 : 1  ω6c) were identified as the predominant fatty acids. The DNA G+C content and digital DNA-DNA relatedness between strain M2^T and K. sediminis F02^T were 60.7 mol% and 19.5 %, respectively. Phosphatidylglycerol and phosphatidylethanolamine were identified as the major polar lipids. Thus, polyphasic characterization revealed that strain M2^T represents a novel species in the genus Kineobactrum, for which the name Kineobactrum salinum sp. nov. is proposed. The type strain is M2^T (=KCTC 72815^T=VTCC 910108^T).

Formosa sediminum sp. nov., a starch-degrading bacterium isolated from marine sediment

A novel bacterium, designated strain PS13^T, was isolated from marine sediment collected from the coast of Jeju Island. Strain PS13^T was a Gram stain-negative, catalase- and oxidase-positive, aerobic, yellow-pigmented, motile by gliding, and rod-shaped bacterium. Strain PS13^T grew optimally at 25 °C and pH 8.0 and in the presence of 3 % (w/v) NaCl. Results of phylogenetic analysis based on 16S rRNA gene sequences showed that strain PS13^T belonged to the genus Formosa and was closely related to Formosa algae KMM3553^T (98.3 % sequence similarity). The DNA-DNA relatedness (17.3-21.8 %) and average nucleotide identity (83.6-84.6 %) values clearly indicated that strain PS13^T represents a distinct species of the genus Formosa. The major fatty acids were C_15 : 0 iso, C_16 : 1 ω6c/C_16 : 1 ω7c and C_15 : 1 iso G. The genomic DNA G+C content of the strain PS13^T was 32.2 mol%. On the basis of polyphasic characteristics, it is suggested that strain PS13^T be assigned to the genus Formosa as the type strain of a novel species, for which the name Formosa sediminum PS13^T (=KCCM 43301^T=CECT 9918^T) sp. nov. is proposed.

Microbial Communities of Polymetallic Deposits' Acidic Ecosystems of Continental Climatic Zone With High Temperature Contrasts

Acid mine drainage (AMD) systems are globally widespread and are an important source of metal pollution in riverine and coastal systems. Microbial AMD communities have been extensively studied for their ability to thrive under extremely acidic conditions and for their immense contribution to the dissolution of metal ores. However, little is known on microbial inhabitants of AMD systems subjected to extremely contrasting continental seasonal temperature patterns as opposed to maritime climate zones, experiencing much weaker annual temperature variations. Here, we investigated three types of AMD sites in Eastern Transbaikalia (Russia). In this region, all surface water bodies undergo a deep and long (up to 6 months) freezing, with seasonal temperatures varying between -33 and +24°C, which starkly contrasts the common well-studied AMD environments. We sampled acidic pit lake (Sherlovaya Gora site) located in the area of a polymetallic deposit, acidic drainage water from Bugdaya gold-molybdenum-tungsten deposit and Ulan-Bulak natural acidic spring. These systems showed the abundance of bacteria-derived reads mostly affiliated with Actinobacteria, Acidobacteria, Alpha- and Gammaproteobacteria, chloroplasts, Chloroflexi, Bacteroidetes, and Firmicutes. Furthermore, candidate taxa "Ca. Saccharibacteria" (previously known as TM7), "Ca. Parcubacteria" (OD1) and WPS-2 were represented in substantial quantities (10-20%). Heterotrophy and iron redox cycling can be considered as central processes of carbon and energy flow for majority of detected bacterial taxa. Archaea were detected in low numbers, with Terrestrial Miscellaneous Euryarchaeal Group (TMEG), to be most abundant (3%) in acidic spring Ulan-Bulak. Composition of these communities was found to be typical in comparison to other AMD sites; however, certain groups (as Ignavibacteriae) could be specifically associated with this area. This study provides insight into the microbial diversity patterns in acidic ecosystems formed in areas of polymetallic deposits in extreme continental climate zone with contrasting temperature parameters.

Arthrobacter dokdonellae sp. nov., isolated from a plant of the genus Campanula

A Gram-stain-positive, oxidase- and catalase-positive motile, aerobic, and rod-shaped bacterial strain, designated as DCT-5^T, was isolated from a native plant belonging to the genus Campanula at Dokdo island, Republic of Korea. Growth of the strain DCT-5^T was observed at 15-37°C (optimum 30°C) on R2A broth, pH 6.0-8.0 (optimum 7.0), and 0-5% (w/v) NaCl concentration (optimum 0%). The 16S rRNA gene sequence analysis revealed that strain DCT-5^T was most closely related to Arthrobacter silviterrae KIS14-16^T, Arthrobacter livingstonensis LI2^T, Arthrobacter stackebrandtii CCM 2783^T, Arthrobacter cryoconiti Cr6-08^T, Arthrobacter ramosus CCM 1646^T, and Arthrobacter psychrochitiniphilus GP3^T with pairwise sequence similarities of 98.76%, 97.47%, 97.25%, 97.11%, 97.11%, and 97.00%, respectively. The DNA G+C content of strain DCT-5^T was 64.7 mol%, and its DNA-DNA relatedness values with A. silviterrae KIS14-16^T, A. livingstonensis LI2^T, A. stackebrandtii CCM 2783^T, A. psychrochitiniphilus GP3^T, A. ramosus CCM 1646^T, and A. cryoconiti Cr6-08^T were 32.57 ± 2.02%, 28.75 ± 0.88%, 31.93 ± 1.15%, 34.73 ± 1.86%, 29.12 ± 1.56%, and 27.23 ± 0.88%, respectively. The major quinone was MK-9(H₂) and major fatty acids were anteiso-C_15:0, anteiso-C_17:0, iso-C_15:0, and iso-C_16:0. The polar lipids were diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), phosphatidylinositol (PI), unidentified glycolipid (GL), two unidentified aminophospholipids (APLs), and three unidentified lipids (Ls). The peptidoglycan type was A3α. On the basis of phenotypic, phylogenetic, genotypic, and chemotaxonomic characteristics, strain DCT-5^T represents a novel species of the genus Arthrobacter, for which the name Arthrobacter dokdonellae sp. nov. is proposed. The type strain is DCT-5^T (= KCTC 49189^T = LMG 31284^T).

Pusillimonas thiosulfatoxidans sp. nov., a thiosulfate oxidizer isolated from activated sludge

A Gram-stain-negative, motile bacterium, designated strain YE3T, was isolated from activated sludge obtained from a municipal wastewater treatment plant in Daejeon Metropolitan City, Republic of Korea. The cells were oxidase- and catalase-positive, and grew under aerobic conditions at 10–40 °C (optimum, 30 °C), with 1.0–8.0 % (w/v) NaCl (1.0 %) and at pH 5.5–9.0 (pH 7.0). Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain YE3T was most closely related to Pusillimonas harenae KACC 14927T (98.2 % sequence similarity) and Pusillimonas ginsengisoli KCTC 22046T (98.0 %). DNA–DNA relatedness values for strain YE3T and P. harenae KACC 14927T, P. ginsengisoli KCTC 22046T and P. soli KCTC 22455T were 28.7±2.27 %, 21.3±1.16 %, and 14.0±0.67 %, respectively. The genomic G+C content of the type strain YE3T was 59.3 mol%, as determined by whole-genome sequencing. The dominant fatty acids were C16 : 0 (39.2 %) and C17 : 0cyclo (37.5 %). The major polar lipids of strain YE3T were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. Two aminophospholipids and four unidentified lipids were also detected. Furthermore, strain YE3T was able to oxidize thiosulfate under heterotrophic conditions. Based on the phenotypic, genotypic, chemotaxonomic and phylogenetic analyses, strain YE3T represents a novel species of the genus Pusillimonas , for which the name Pusillimonas thiosulfatoxidans sp. nov. is proposed. The type strain is YE3T (=KCTC 62737T=NBRC 113113T).

Paenibacillus seodonensis sp. nov., isolated from a plant of the genus Campanula

Strain DCT-19^T, representing a Gram-stain-positive, rodshaped, aerobic bacterium, was isolated from a native plant belonging to the genus Campanula on Dokdo, the Republic of Korea. Comparative analysis of the 16S rRNA gene sequence showed that this strain was closely related to Paenibacillus amylolyticus NRRL NRS-290^T (98.6%, 16S rRNA gene sequence similarity), Paenibacillus tundrae A10b^T (98.1%), and Paenibacillus xylanexedens NRRL B-51090^T (97.6%). DNADNA hybridization indicated that this strain had relatively low levels of DNA-DNA relatedness with P. amylolyticus NRRL NRS-290^T (30.0%), P. xylanexedens NRRL B-51090^T (29.0%), and P. tundrae A10b^T (24.5%). Additionally, the genomic DNA G + C content of DCT-19^T was 44.8%. The isolated strain grew at pH 6.0-8.0 (optimum, pH 7.0), 0-4% (w/v) NaCl (optimum, 0%), and a temperature of 15-45°C (optimum 25-30°C). The sole respiratory quinone in the strain was menaquinone-7, and the predominant fatty acids were C_15:0 anteiso, C_16:0 iso, and C_16:0. In addition, the major polar lipids were diphosphatidylglycerol and phosphatidylethanolamine. Based on its phenotypic properties, genotypic distinctiveness, and chemotaxonomic features, strain DCT-19^T is proposed as a novel species in the genus Paenibacillus, for which the name Paenibacillus seodonensis sp. nov. is proposed (=KCTC 43009^T =LMG 30888^T). The type strain of Paenibacillus seodonensis is DCT-19^T.

Rhodanobacter hydrolyticus sp. nov., a novel DNA- and tyrosine-hydrolysing gammaproteobacterium isolated from forest soil

A bacterial isolate, designated G-5-5^T, was isolated from forest soil at Kyonggi University. Strain G-5-5^T was acid-tolerant and alkali-tolerant. Cells were strictly aerobic, Gram-stain-negative, catalase- and oxidase-positive, non-motile, non-spore-forming, rod-shaped, and yellow-coloured. Strain G-5-5^T hydrolysed DNA and tyrosine; assimilated d-glucose, maltose, N-acetyl-glucosamine and l-fucose; and tolerated only 0.5 % NaCl (w/v). Phylogenetic analysis based on its 16S rRNA gene sequence revealed that strain G-5-5^T formed a lineage within the family Rhodanobacteraceae and that it grouped with but was distinct from various members of the genus Rhodanobacter. The closest member was Rhodanobacter umsongensis GR24-2^T (97.8 % sequence similarity). The sole respiratory quinone was Q-8. The major polar lipids of strain G-5-5^T were phosphatidylethanolamine, phosphatidyl-N-methylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The major cellular fatty acids were summed feature 9 (iso-C17 : 1ω9c and/or C16 : 0 10-methyl), iso-C15 : 0, iso-C17 : 0, iso-C16 : 0 and anteiso-C15 : 0. The DNA G+C content of strain G-5-5^T was 64.1 mol%. DNA-DNA hybridization relatedness between strain G-5-5^T and other close members of the genus Rhodanobacter ranged from 19 % to 45 %. On the basis of the polyphasic characterization and phylogenetic analyses, strain G-5-5^T represents a novel species of the genus Rhodanobacter, for which the name Rhodanobacter hydrolyticus sp. nov. is proposed. The type strain is G-5-5^T (=KEMB 9005-533^T=KACC 19113^T=NBRC 112685^T).

Burkholderia alba sp. nov., isolated from a soil sample on Halla mountain in Jeju island

A rod-shaped, round and white colony-forming strain AD18^T was isolated from the soil on Halla mountain in Jeju Island, Republic of Korea. Comparative analysis of 16S rRNA gene sequence revealed that this strain was closely related to Burkholderia oklahomensis C6786^T (98.8%), Burkholderia thailandensis KCTC 23190^T (98.5%). DNA-DNA relatedness (14.6%) indicated that the strain AD18^T represents a distinct species that is separate from B. oklahomensis C6786^T. The isolate grew at pH 5.0-9.0 (optimum, pH 7.0), 0-3% (w/v) NaCl (optimum, 0%), and temperature 10-40°C (optimum 35°C). The sole quinone of the strain was Q-8, and the predominant fatty acids were C_16:0, C_17:0 cyclo, and C_19:0 cyclo ω8c. The genomic DNA G + C content of AD18T was 65.6 mol%. Based on these findings, strain AD18^T is proposed to be a novel species in the genus Burkholderia, for which the name Burkholderia alba sp. nov. is proposed (= KCCM 43268^T = JCM 32403^T). The type strain is AD18^T.

Soil microbial community responses to acid exposure and neutralization treatment

Changes in microbial community induced by acid shock were studied in the context of potential release of acids to the environment due to chemical accidents. The responses of microbial communities in three different soils to the exposure to sulfuric or hydrofluoric acid and to the subsequent neutralization treatment were investigated as functions of acid concentration and exposure time by using 16S-rRNA gene based pyrosequencing and DGGE (Denaturing Gradient Gel Electrophoresis). Measurements of soil pH and dissolved ion concentrations revealed that the added acids were neutralized to different degrees, depending on the mineral composition and soil texture. Hydrofluoric acid was more effectively neutralized by the soils, compared with sulfuric acid at the same normality. Gram-negative ß-Proteobacteria were shown to be the most acid-sensitive bacterial strains, while spore-forming Gram-positive Bacilli were the most acid-tolerant. The results of this study suggest that the Gram-positive to Gram-negative bacterial ratio may serve as an effective bio-indicator in assessing the impact of the acid shock on the microbial community. Neutralization treatments helped recover the ratio closer to their original values. The findings of this study show that microbial community changes as well as geochemical changes such as pH and dissolved ion concentrations need to be considered in estimating the impact of an acid spill, in selecting an optimal remediation strategy, and in deciding when to end remedial actions at the acid spill impacted site.

Halomonas aestuarii sp. nov., a moderately halophilic bacterium isolated from a tidal flat

Strain Hb3^T was isolated from a tidal flat in Jeollabuk-do Gunsan, Republic of Korea. Cells were Gram-stain-negative, oxidase- and catalase-positive, rod-shaped and motile. The strain grew optimally at 25-35 °C, at pH 6.0-6.5 and with 3.0-10.0 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain Hb3^T belonged to the genus Halomonas. Strain Hb3^T was related most closely to Halomonas ventosae Al12^T (98.6 % 16S rRNA gene sequence similarity), Halomonas denitrificans M29^T (98.6 %) and Halomonas saccharevitans AJ275^T (98.4 %). Moreover, multilocus sequence analysis using the gyrB, rpoD and secA genes supported the phylogenetic position of strain Hb3^T. The genomic G+C content of strain Hb3^T was 67.9 mol%. DNA-DNA hybridization values for strain Hb3^T versus H. ventosae Al12^T, H. denitrificans M29^T and H. saccharevitans AJ275^T were 38.0, 54.5 and 47.4 %, respectively. The major quinone was ubiquinone Q-9 and the major fatty acids were C18 : 1ω7c, summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c), C16 : 0 and C19 : 0 cyclo ω8c. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, amino lipid, six unidentified phospholipids and an unidentified lipid comprised the polar lipid profile. On the basis of the data presented in this report, strain Hb3^T represents a novel species of the genus Halomonas. The name Halomonas aestuarii sp. nov. is proposed for this novel species. The type strain is Hb3^T (=KCTC 52253^T=JCM 31415^T).