Marinobacter qingdaonensis sp. nov., a moderately halotolerant bacterium isolated from intertidal sediment.

A Gram-stain-negative, aerobic, rod-shaped and halotolerant bacterium, designated as strain ASW11-75T, was isolated from intertidal sediments in Qingdao, PR China, and identified using a polyphasic taxonomic approach. Growth of strain ASW11-75T occurred at 10-45 °C (optimum, 37 °C), pH 6.5-9.0 (optimum, pH 8.0) and 0.5-18.0 % NaCl concentrations (optimum, 2.5 %). Phylogenetic analyses based on 16S rRNA gene sequences and 1179 single-copy orthologous clusters indicated that strain ASW11-75T is affiliated with the genus Marinobacter. Strain ASW11-75T showed highest 16S rRNA gene sequence similarity to 'Marinobacter arenosus' CAU 1620T (98.5 %). The digital DNA-DNA hybridization and average nucleotide identity values between strain ASW11-75T and its closely related strains (Marinobacter salarius R9SW1T, Marinobacter similis A3d10T, 'Marinobacter arenosus' CAU 1620T, Marinobacter sediminum R65T, Marinobacter salinus Hb8T, Marinobacter alexandrii LZ-8T and Marinobacter nauticus ATCC 49840T) were 19.8-24.5 % and 76.6-80.7 %, respectively. The predominant cellular fatty acids were C16 : 0, C18 : 1 ω9c and C16 : 0 N alcohol. The polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified aminophospholipid and two unidentified lipids. The major isoprenoid quinone was ubiquinone-9. The genomic DNA G+C content was 62.2 mol%. Based on genomic and gene function analysis, strain ASW11-75T had lower protein isoelectric points with higher ratios of acidic residues to basic residues and possessed genes related to ion transport and organic osmoprotectant uptake, implying its potential tolerance to salt. The results of polyphasic characterization indicated strain ASW11-75T represents a novel Marinobacter species, for which the name Marinobacter qingdaonensis sp. nov. with the type strain ASW11-75T is proposed. The type strain is ASW11-75T (=KCTC 82497T=MCCC 1K05587T).

Influence of Cupric (Cu2+) Ions on the Iron Oxidation Mechanism by DNA-Binding Protein from Starved Cells (Dps) from Marinobacter nauticus.

Dps proteins (DNA-binding proteins from starved cells) are multifunctional stress defense proteins from the Ferritin family expressed in Prokarya during starvation and/or acute oxidative stress. Besides shielding bacterial DNA through binding and condensation, Dps proteins protect the cell from reactive oxygen species by oxidizing and storing ferrous ions within their cavity, using either hydrogen peroxide or molecular oxygen as the co-substrate, thus reducing the toxic effects of Fenton reactions. Interestingly, the interaction between Dps and transition metals (other than iron) is a known but relatively uncharacterized phenomenon. The impact of non-iron metals on the structure and function of Dps proteins is a current topic of research. This work focuses on the interaction between the Dps from Marinobacter nauticus (a marine facultative anaerobe bacterium capable of degrading petroleum hydrocarbons) and the cupric ion (Cu2+), one of the transition metals of greater biological relevance. Results obtained using electron paramagnetic resonance (EPR), Mössbauer and UV/Visible spectroscopies revealed that Cu2+ ions bind to specific binding sites in Dps, exerting a rate-enhancing effect on the ferroxidation reaction in the presence of molecular oxygen and directly oxidizing ferrous ions when no other co-substrate is present, in a yet uncharacterized redox reaction. This prompts additional research on the catalytic properties of Dps proteins.

Immunostimulant properties of full-length and truncated Marinobacter algicola flagellins, and their effects against viral hemorrhagic septicemia virus (VHSV) in trout.

Adjuvants that would help optimize fish vaccines against bacterial and viral pathogens are highly demanded by the aquaculture sector. Flagellin has been proposed as an immunostimulant and an adjuvant for more than a decade. However, the adjuvant ability of flagellins with hypervariable region deleted is still unclear in fish. In this study, we evaluated the immune-stimulating capacity of two recombinant flagellins, the wild-type flagellin F from Marinobacter algicola and a version with the hypervariable region deleted (FredV2), to induce the transcription of a wide range of immune genes using two rainbow trout cell lines: a monocyte/macrophage-cell line (RTS-11) and an epithelial cell line from intestine (RTgutGC). Additionally, we studied the capacity of both flagellins to limit the replication of viral hemorrhagic septicemia virus (VHSV) on the RTgutGC cell line. Our results demonstrated that both recombinant flagellins can significantly increase the transcription of IL-1ß1, IL-6, and IL-8 in both cell lines. However, other cytokines such as IFNγ1, and TNFα or antimicrobial peptides such as hepcidin were induced by both flagellins in RTgutGC but not in RTS-11 cells. Furthermore, both flagellins were capable of reducing the replication of VHSV in RTgutGC cells. Although the immunostimulatory and the antiviral capacities exerted by F were slightly more potent than those obtained with FredV2, the effects were retained after losing the hypervariable region. Our results provide new information on the immunostimulating and antiviral capacities of flagellins that point to their potential as suitable adjuvants for the future optimization of vaccines in aquaculture.

Mesopelagic microbial community dynamics in response to increasing oil and Corexit 9500 concentrations.

Marine microbial communities play an important role in biodegradation of subsurface plumes of oil that form after oil is accidentally released from a seafloor wellhead. The response of these mesopelagic microbial communities to the application of chemical dispersants following oil spills remains a debated topic. While there is evidence that contrasting results in some previous work may be due to differences in dosage between studies, the impacts of these differences on mesopelagic microbial community composition remains unconstrained. To answer this open question, we exposed a mesopelagic microbial community from the Gulf of Mexico to oil alone, three concentrations of oil dispersed with Corexit 9500, and three concentrations of Corexit 9500 alone over long periods of time. We analyzed changes in hydrocarbon chemistry, cell abundance, and microbial community composition at zero, three and six weeks. The lowest concentration of dispersed oil yielded hydrocarbon concentrations lower than oil alone and microbial community composition more similar to control seawater than any other treatments with oil or dispersant. Higher concentrations of dispersed oil resulted in higher concentrations of microbe-oil microaggregates and similar microbial composition to the oil alone treatment. The genus Colwellia was more abundant when exposed to multiple concentrations of dispersed oil, but not when exposed to dispersant alone. Conversely, the most abundant Marinobacter amplicon sequence variant (ASV) was not influenced by dispersant when oil was present and showed an inverse relationship to the summed abundance of Alcanivorax ASVs. As a whole, the data presented here show that the concentration of oil strongly impacts microbial community response, more so than the presence of dispersant, confirming the importance of the concentrations of both oil and dispersant in considering the design and interpretation of results for oil spill simulation experiments.

Marinobacter mangrovi sp. nov., isolated from mangrove sediment.

A novel marine bacterium, designated strain CHFG3-1-5T, was isolated from mangrove sediment sampled at Jiulong River estuary, Fujian, PR China. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain CHFG3-1-5T belonged to the genus Marinobacter, with the highest sequence similarity to Marinobacter segnicrescens SS011B1-4T (97.6%), followed by Marinobacter nanhaiticus D15-8WT (97.5%), Marinobacter bohaiensis T17T (97.1%) and Marinobacter hydrocarbonoclasticus SP.17T (90.6%). The bacterium was Gram-stain-negative, facultative anaerobic, oxidase- and catalase-positive, rod-shaped and motile with a polar flagellum. Strain CHFG3-1-5T grew optimally at 32-37 °C, pH 6.0-8.0 and in the presence of 2.0-3.0% (w/v) NaCl. The G+C content of the chromosomal DNA was 61.1 mol%. The major respiratory quinone was determined to be Q-9. The principal fatty acids were C16 : 0, summed feature 3 (C16 : 1 ω7c/ω6c), C12 : 0, summed feature 9 (C17 : 1 iso ω9c and/or C16 : 0 10-methyl), C12 : 0 3-OH and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c). The polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, three phospholipids, one glycolipid and two aminolipids. The average nucleotide identity and digital DNA-DNA hybridization values among the genomes of strain CHFG3-1-5T and the reference strains were 73.4-79.4 and 19.6-22.4%, respectively. Like many other species reported in the genus Marinobacter, strain CHFG3-1-5T was able to oxidise iron. The combined genotypic and phenotypic data showed that strain CHFG3-1-5T represents a novel species within the genus Marinobacter, for which the name Marinobacter mangrovi sp. nov. is proposed, with the type strain CHFG3-1-5T (=MCCC 1A18306T=KCTC 82398T).

Detection of hydrocarbon-degrading bacteria on deepwater corals of the northeast Atlantic using CARD-FISH.

Recently, studies have begun to identify oil-degrading bacteria and host-taxon specific bacterial assemblages associated with the coral holobiont, including deep-sea cold-water corals, which are thought to provide metabolic functions and additional carbon sources to their coral hosts. Here, we describe the identification of Marinobacter on the soft tissue of Lophelia pertusa coral polyps by Catalyzed Reporter Deposition Fluorescence in situ Hybridization (CARD-FISH). L. pertusa samples from three reef sites in the northeast Atlantic (Logachev, Mingulay and Pisces) were collected at depth by vacuum seal to eliminate contamination issues. After decalcification, histological processing and sagittal sectioning of the soft coral polyp tissues, the 16S rRNA-targeted oligonucleotide HRP-labelled probe Mrb-0625-a, and Cyanine 3 (Cy3)-labelled tyramides, were used to identify members of the hydrocarbon-degrading genus Marinobacter. Mrb-0625-a-hybridized bacterial cell signals were detected in different anatomical sites of all polyps collected from each of the three reef sites, suggesting a close, possibly intimate, association between them, but the purpose of which remains unknown. We posit that Marinobacter, and possibly other hydrocarbon-degrading bacteria associated with Lophelia, may confer the coral with the ability to cope with toxic levels of hydrocarbons in regions of natural oil seepage and where there is an active oil and gas industry presence.

Structural features and stability of apo- and holo-forms of a simple iron-sulfur protein.

Iron-sulfur centers are widespread in living organisms, mostly performing electron transfer functions, either in electron transfer chains or as part of multi-enzymatic complexes, while being also present in enzyme active sites, handling substrate catalysis. Rubredoxin is the simplest iron-sulfur containing protein constituted by a single polypeptide chain of 50 to 60 amino acids, of which four cysteine residues are responsible for metal binding in a tetrahedral coordination sphere. In this manuscript we explore the structure and stability of both apo- and holo-forms of a Rubredoxin from Marinobacter hydrocarbonoclasticus using Synchrotron Radiation Circular Dichroism (SRCD) in combination with other biochemical and spectroscopic techniques. The results are consistent with a holo-protein form containing a monomeric iron center with UV-visible maxima at 760, 578, 494, 386, 356 and 279 nm, an intense EPR resonance with a g value around 4.3 and Mössbauer spectroscopy parameters of δ equal to 0.69 mm/s and ΔEQ equal to 3.25 mm/s, for the ferrous reconstituted state. SRCD data, obtained for the first time for the apo-form, show a quite defined structure with ∆ε maximum at 191 nm and minima at 203 and 231 nm. Most significantly, the presence of isosbestic points at 189 and 228 nm made the interconversion between the two stable apo- and holo-form solution structures clear. SRCD temperature dependence data shows that for both forms the denaturation process proceeds through an intermediate species.

Marinobacter alexandrii sp. nov., a novel yellow-pigmented and algae growth-promoting bacterium isolated from marine phycosphere microbiota.

The marine phycosphere harbors unique cross-kingdom associations with ecological relevance. During investigating the diversity of phycosphere microbiota of marine harmful algal blooms dinoflagellates, a faint yellow-pigmented bacterium, designated as strain LZ-8, was isolated from paralytic shellfish poisoning toxin-producing dinoflagellate Alexandrium catenella LZT09. The new isolate appeared to have growth-promoting potential toward its algal host. Molecular analysis using 16S rRNA gene, housekeeping rpoD gene and whole-genome sequence comparison indicated that strain LZ-8T was a novel gammaproteobacterium of the family Alteromonadaceae. The major fatty acids of strain LZ-8T were C16:0, C18:1 ω9c, C12:0 3-OH, summed feature 3, C16:1 ω9c, C12:0 and summed feature 9. The major isoprenoid quinone was Q-9. Polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, unidentified phospholipid, two unidentified aminolipids and six unidentified polar lipids. The genomic DNA G+C content was 57.36 mol%. Based on genome sequencing, several biosynthetic gene clusters responsible for bacterial biosynthesis of carotenoids and siderophores that may involve in algae-bacterial interactions were identified in the genome of strain LZ-8T. The polyphasic characterization indicated that strain LZ-8T represents a novel Marinobacter species. The name Marinobacter alexandrii sp. nov., type strain LZ-8T (= CCTCC AB 2018386T = KCTC 72198T) is proposed.

Marinobacter caseinilyticus sp. nov., Isolated from Saline Soil.

A Gram-stain-negative, motile, aerobic, rod-shaped bacterium with flagella, designated M3-13T, was isolated from a saline soil in Zhoushan, China. According to phylogenetic analysis based on 16S rRNA gene sequences, strain M3-13T was assigned to the genus Marinobacter with highest 16S rRNA gene sequence similarity of 97.7% to Marinobacter maroccanus LMG 30466T, followed by Marinobacter sediminum R65 T (97.5%) and M. salsuginis SD-14BT (97.2%). Digital DNA-DNA hybridization (DDH) and average nucleotide identity (ANI) were determined to evaluate the genomic relationship between strain M3-13T and M. maroccanus LMG 30466T. Digital DDH estimation (19.8%) as well as ANI (72.98%) proved the dissimilarity of strain M3-13T. Optimal growth of the strain M3-13T was at 28-30 °C and at pH 8.0-8.5, in the presence of 3-6% (w/v) NaCl. The major fatty acids detected in strain M3-13T were C16:1 ω7c/C16:1 ω6c, C16:0, C18:1ω7c/C18:1 ω6c and C12:03-OH, and the predominant respiratory quinone was ubiquinone-9. The major polar lipids included diphosphatidyglycerol, phosphatidylglycerol, phosphatidylethanolamine, one unidentified aminophosphoglycolipid and one unidentified phosphoglycolipid. The DNA G+C content was 56.6%. A phylogenetic analysis based on 16S rRNA gene sequences showed that strain M3-13T belongs to the genus Marinobacter. Based on the polyphasic taxonomic characterization, strain M3-13T is considered to represent a novel species of the genus Marinobacter, for which the name Marinobacter caseinlyticus sp. nov. is proposed (type strain M3-13T = MCCC 1K04560T = KCTC 72043T).

Nanoliter scale electrochemistry of natural and engineered electroactive bacteria.

Bacterial extracellular electron transfer (EET) is envisioned for use in applied biotechnologies, necessitating electrochemical characterization of natural and engineered electroactive biofilms under conditions similar to the target application, including small-scale biosensing or biosynthesis platforms, which is often distinct from standard 100 mL-scale stirred-batch bioelectrochemical test platforms used in the laboratory. Here, we adapted an eight chamber, nanoliter volume (500 nL) electrochemical flow cell to grow biofilms of both natural (Biocathode MCL community, Marinobacter atlanticus, and Shewanella oneidensis MR1) or genetically modified (S. oneidensis ΔMtr and S. oneidensis ΔMtr + pLB2) electroactive bacteria on electrodes held at a constant potential. Maximum current density achieved by unmodified strains was similar between the nano- and milliliter-scale reactors. However, S. oneidensis biofilms engineered to activate EET upon exposure to 2,4-diacetylphloroglucinol (DAPG) produced current at wild-type levels in the stirred-batch reactor, but not in the nanoliter flow cell. We hypothesize this was due to differences in mass transport of DAPG, naturally-produced soluble redox mediators, and oxygen between the two reactor types. Results presented here demonstrate, for the first time, nanoliter scale chronoamperometry and cyclic voltammetry of a range of electroactive bacteria in a three-electrode reactor system towards development of miniaturized, and potentially high throughput, bioelectrochemical platforms.

Bacterial community analysis of biofilm on API 5LX carbon steel in an oil reservoir environment.

This study aimed to characterize the biofilm microbial community that causes corrosion of API 5LX carbon steel. API 5LX carbon steel coupons were incubated with raw produced water collected from two oil reservoir stations or filter-sterilized produced water. Biofilm 16S rRNA amplicon sequencing revealed that the bacterial community present in the biofilm was dominated by Proteobacteria, including Marinobacter hydrocarbonoclaustics and Marinobacter alkaliphilus. Electrochemical analysis such as impedance and polarization results indicated that Proteobacteria biofilm accelerated corrosion by ~ twofold (2.1 ± 0.61 mm/years) or ~ fourfold (~ 3.7 ± 0.42 mm/years) when compared to the control treatment (0.95 ± 0.1 mm/years). Scanning electron and atomic force microscopy revealed the presence of a thick biofilm and pitting corrosion. X-ray diffraction revealed higher amounts of the corrosion products Fe2O3, γ-FeOOH, and α-FeOOH, and confirmed that the microbial biofilm strongly oxidized the iron and contributed to the acceleration of corrosion of carbon metal API 5LX.

Marinobacter halodurans sp. nov., a halophilic bacterium isolated from sediment of a salt flat.

A Gram-staining-negative, aerobic, cream-coloured, marine bacterium, with rod-shaped cells, designated strain YJ-S3-2T, was isolated from salt flat sediment of Yongyu-do, Republic of Korea. YJ-S3-2T grew at pH 5.0-9.0 (optimum pH 7.0), 4-45 °C (optimum 30 °C) and with 1-18 % (w/v) NaCl (optimum 6 %). The results of 16S rRNA gene sequence analysis indicated that YJ-S3-2T was closely related to Marinobacter segnicrescens SS011B1-4T (97.0 %) followed by, 'Marinobacter nanhaiticus' D15-8W (96.7 %), Marinobacter bryozoorum 50-11T (96.7 %), Marinobacter koreensis DSMZ 179240T T (96.5 %) and Marinobacter bohaiensis T17T (96.5 %). The average nucleotide identity (ANI) and the genome to genome distance calculator (GGDC) estimate values between YJ-S3-2T and related type strains were 73.7-79.8 and 19.9-22.5 %, and also 73.5 and 20.7 % with Marinobacter hydrocarbonoclasticus. YJ-S3-2T was characterized as having Q-9 as the predominant respiratory quinone and the principal fatty acids (>10 %) were C16 : 0 (22.3 %), summed feature 9 (C17 : 1iso ω9c/C16 : 0 10-methyl, 13.8 %) and 3 (C16 : 1ω7c/C16 : 1ω6c, 11.9 %). The polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, two unidentified aminolipids and two unidentified phospholipids. The DNA G+C content of YJ-S3-2T is 60.9 mol%. On the basis of the polyphasic taxonomic evidence presented in this study, YJ-S3-2T should be classified as representing a novel species within the genus Marinobacter, for which name Marinobacter halodurans sp. nov. is proposed, with the type strain YJ-S3-2T (=KACC 19883T=KCTC 62937T=JCM 33109T).

Protective effects of culture extracts (CB08035-SCA and CB08035-SYP) from Marinobacter hydrocarbonoclasticus (strain CB08035) against oxidant-induced stress in human colon carcinoma Caco-2 cells.

The present study investigated the effect of culture extracts (CB08035-SCA and CB08035-SYP) from Marinobacter hydrocarbonoclasticus (strain CB08035) on cell viability and the potential protective effects attributed to molecular mechanisms underlying antioxidant response to survive oxidative stress injuries. Caco-2 cells were submitted to oxidative stress by treatment with tert-butyl hydroperoxide (t-BOOH). Both extracts prevented cell damage and enhanced activity of antioxidant defenses (NQO1 and GST activities and GSH levels) reduced by treatment with t-BOOH. Increased ROS and caspase 3/7 activity induced by t-BOOH were dose-dependently prevented when cells were treated with the extracts. CB08035-SCA caused up-regulation of Nrf2, AKT1 and Bcl-2 gene expressions. Moreover, CB08035-SCA and CB08035-SYP treatments reduced significantly Bax, BNIP3, APAF1, ERK1, JNK1, MAPK1, NFκB1, TNFα, IL-6, IL-1ß and HO-1 gene expressions of apoptosis, proinflammation and oxidative stress induced by t-BOOH. CB08035-SCA and CB08035-SYP CPE extracts confer a significant protection against oxidative insults to cells. Our results show that culture extracts CB08035-SCA and CB08035-SYP from M. hydrocarbonoclasticus (strain CB08035) appeared to have antioxidant potential, based on their ability to protect antioxidant enzymes and mRNA gene expressions linked to apoptosis/oxidative pathways. These results suggest that culture extracts CB08035-SCA and CB08035-SYP can be a potential ingredient in the pharmaceutical and cosmeceutical industries.

Marinobacter salinexigens sp. nov., a marine bacterium isolated from hadal seawater of the Mariana Trench.

A Gram-stain-negative, strictly aerobic, non-motile and rod-shaped bacterium, designated ZYF650T, was isolated from the hadal seawater (9600 m) of the Mariana Trench. Results of phylogenetic analysis based on 16S rRNA gene sequences indicated that ZYF650T formed a lineage within the family Alteromonadaceae that was distinct from the most closely related species Marinobacter mobilis and Marinobacter nitratireducens with 16S rRNA gene sequences similarities of 98.0 and 97.7 %, respectively. Strain ZYF650T showed average nucleotide identity values of 75.7 % with Marinobacter hydrocarbonoclasticus, 73.3 % with Marinobacter mobilis and 79.3 % with Marinobacter nitratireducens, and DNA-DNAhybridization values of 21.5, 21.3 and 22.0 % with M. hydrocarbonoclasticus, M. mobilis and M. nitratireducens, respectively, which were lower than the threshold for species delineation. Strain ZYF650T grew with 0-14 % (w/v) NaCl (optimum, 7-8 %) at a temperature range of 10-45 °C (optimum, 28 °C) and pH 6.0-9.5 (optimum, pH 7.0-8.0). The sole respiratory quinone was ubiquinone-9 (Q-9). The polar lipids in ZYF650T comprised phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, three unidentified polar lipids, two unidentified aminolipids and two phospholipids. The predominant fatty acids (more than 10 % of total fatty acids) were C18 : 1 ω9c (21.9 %), C16 : 0 (21.7 %), C12 : 0 3-OH (14.0 %), C16 : 1 ω9c (13.2 %) and C12 : 0 (12.2 %). The DNA G+C content of strain ZYF650T was 55.6 %. On the basis of polyphasic taxonomic analysis, strain ZY650T is considered to represent a novel specie of the genus Marinobacter in the family Alteromonadaceae, for which the name Marinobacter salinexigens sp. nov. is proposed. The type strain is ZYF650T (=JCM 33013T=MCCC 1K03552T).

Marinobacter changyiensis, sp. nov., isolated from offshore sediment.

An aerobic, Gram-stain-negative bacterium, designated CLL7-20T, was isolated from a marine sediment sample from offshore of Changyi, Shandong Province, China. Cells of strain CLL7-20T were rod-shaped, motile with one or more polar flagella, and grew optimally at pH 7.0, at 28 °C and with 3 % (w/v) NaCl. The principal fatty acids of strain CLL7-20T were C16 : 0 and summed feature 3 (C16 : 1 ω7c/C16 : 1 ω6c). The main polar lipids of strain CLL7-20T were phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG) and an unidentified aminolipid (AL). Strain CLL7-20T contained Q-9 as the major respiratory quinone. The G+C content of its genomic DNA was 56.2 mol%. Phylogenetically, strain CLL7-20T branched within the genus Marinobacter, with M. daqiaonensis YCSA40T being its closest phylogenetic relative (96.7 % 16S rRNA gene sequence similarity), followed by M. sediminum R65T (96.6 %). Average nucleotide identity and in silico DNA-DNA hybridization values between strain CLL7-20T and the closest related reference strains were 73.2% and 19.8 %, respectively. On the basis of its phenotypic, phylogenetic and chemotaxonomic characteristics, we suggest that strain CLL7-20T (=MCCC 1A14855T=KCTC 72664T) is the type strain of a novel species in the genus Marinobacter, for which the name Marinobacter changyiensis sp. nov. is proposed. Based on the genomic analysis, siderophore genes were found from strain CLL7-20T, which indicate its potential as a promising alternative to chemical fertilizers in iron-limitated environments such as saline soils.

An induced corrosion inhibition of X80 steel by using marine bacterium Marinobacter salsuginis.

The corrosion behaviour of X80 pipeline steel was studied in a simulated marine environment inoculated with marine bacterium Marinobacter salsuginis. The electrochemical results showed that the increase in linear polarization resistance, charge transfer resistance, and the decrease in corrosion current density of the X80 pipeline steel immersed in the biotic medium indicated its high corrosion resistance compared to those in the abiotic medium. Surface morphological techniques including scanning electron microscopy, confocal laser scanning microscopy and live/dead cells staining were employed to observe the biofilm morphology and bacterial viability after different immersion times. X-ray photoelectron spectroscopy was used to analyse the oxides film formed on the steel surface. The obtained results indicated that the corrosion inhibition efficiency was obviously higher in the biotic medium compared to that in the abiotic medium. The high corrosion resistance of X80 steel in biotic medium was attributed to the formation of biofilm and the development of extracellular polymeric substances (EPS) layer on its surface.

Hydrophobicity-responsive engineered mesoporous silica nanoparticles: application in the delivery of essential nutrients to bacteria combating oil spills.

Facile chemical modification of mesoporous silica particles allows the production of gated reservoir systems capable of hydrophobicity-triggered release. Applied to the delivery of nutrients specifically to an oil phase, the systems developed have been shown to reliably assist the bacterial degradation of hydrocarbons. The gated system developed, made of C18 hydrocarbon chains, is demonstrated to be in a closed collapsed state in an aqueous environment, yet opens up through solvation by lipophilic alkanes and releases its content on contact with the oil phase.

Distribution of dissolved iron and bacteria producing the photoactive siderophore, vibrioferrin, in waters off Southern California and Northern Baja.

Phytoplankton blooms can cause acute effects on marine ecosystems due either to their production of endogenous toxins or to their enormous biomass leading to major impacts on local economies and public health. Despite years of effort, the causes of these Harmful Algal Blooms are still not fully understood. Our hypothesis is that bacteria that produce photoactive siderophores may provide a bioavailable source of iron for phytoplankton which could in turn stimulate algal growth and support bloom dynamics. Here we correlate iron concentrations, phytoplankton cell counts, bacterial cell abundance, and copy numbers for a photoactive siderophore vibrioferrin biosynthesis gene in water samples taken from 2017 cruises in the Gulf of California, and the Pacific Ocean off the coast of northern Baja California as well as during a multiyear sampling at Scripps Pier in San Diego, CA. We find that bacteria producing the photoactive siderophore vibrioferrin, make up a surprisingly high percentage of total bacteria in Pacific/Gulf of California coastal waters (up to 9%). Vibroferrin's unique properties and the widespread prevalence of its bacterial producers suggest that it may contribute significantly to generating bioavailability of iron via photoredox reactions.

Marinobacter profundi sp. nov., a slightly halophilic bacterium isolated from a deep-sea sediment sample of the New Britain Trench.

A piezotolerant, cold-adapted, slightly halophilic bacterium, designated strain PWS21T, was isolated from a deep-sea sediment sample collected from the New Britain Trench. Cells were observed to be Gram-stain negative, rod-shaped, oxidase- and catalase-positive. Growth of the strain was observed at 4-45 °C (optimum 37 °C), at pH 5.0-9.0 (optimum 7.0) and in 0.5-20% (w/v) NaCl (optimum 3-4%). The optimum pressure for growth was 0.1 MPa (megapascal) with tolerance up to 70 MPa. 16S rRNA gene sequence analysis showed that strain PWS21T is closely related to Marinobacter guineae M3BT (98.4%) and Marinobacter lipolyticus SM19T (98.2%). Multilocus sequence analysis (MLSA) based on sequences of housekeeping genes gyrB, recA, atpD, rpoB and rpoD indicates that strain PWS21T represents a distinct evolutionary lineage within the genus Marinobacter. Furthermore, strain PWS21T showed low ANI and diDDH values to the closely related species. The principal fatty acids were identified as C12:0, C12:0 3-OH, C16:1ω9c, C16:0 and C18:1ω9c. Ubiquinone-9 was identified as the major respiratory quinone. The polar lipids were identified as phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), aminophospholipid (APL), two unidentified lipids and an unidentified phospholipid (PL). The G + C content of the genomic DNA was determined to be 60.3 mol%. On the basis of phenotypic, chemotaxonomic and molecular data, we conclude that strain PWS21T represents a novel species of the genus Marinobacter, for which the name Marinobacter profundi sp. nov. is proposed (type strain PWS21T = KCTC 52990T = MCCC 1K03345T).

Marinobacter fuscus sp. nov., a marine bacterium of Gammaproteobacteria isolated from surface seawater.

A Gram-stain-negative bacterium, designated NH169-3T, was isolated from a surface seawater sample of the South China Sea and subjected to a taxonomic polyphasic investigation. Strain NH169-3T was strictly aerobic, non-motile, non-spore-forming and rod-shaped. The colony was 1.0-2.0 mm in diameter after the growth on marine agar at 30 °C for 72 h. The centre of the colony was smooth, circular, convex and brown with a transparent periphery. Strain NH169-3T was able to grow at temperatures between 4-40 °C (optimum, 37 °C), pH 5.5-9.0 (pH 7.5) and with 0-12.5 % (w/v) NaCl (3.0 %). Chemotaxonomic analysis showed that the sole respiratory quinone of strain NH169-3T was ubiquinone 9; major fatty acids were C16 : 0 and C18 : 1ω9c, and major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and one unidentified glycolipid. The DNA G+C content was 52.7 mol%. The comparison of 16S rRNA gene sequences showed that strain NH169-3T was closely related to Marinobacter shengliensis SL013A34A2T with a similarity of 98.0 %. Three phylogenetic trees reconstructed with neighbour-joining, maximum-parsimony and maximum-likelihood methods using 16S rRNA gene sequences showed that strain NH169-3T was grouped into a separated branch with M. shengliensis SL013A34A2T in a clade of the genus Marinobacter and closely related to Marinobacter halophilus JCM 30472T, Marinobacter vinifirmus DSM 17747T and Marinobacter hydrocarbonoclasticus DSM 8798T. Analyses of both phenotypic and phylogenetic properties have suggested that strain NH169-3T was distinctive from species with validly published names in genus Marinobacter. Thus, strain NH169-3T (=MCCC 1K03455T=KCTC 62226T) is proposed as a novel species in genus Marinobacter with the name Marinobacter fuscus sp. nov.