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Applied and Environmental Microbiology

Dongfei Han, Hannes Link, Werner Liesack
Soil microorganisms have to rapidly respond to salt-induced osmotic stress. Type II methanotrophs of the genus Methylocystis are widely distributed in upland soils, but are known to have a low salt tolerance. Here, we tested the ability of Methylocystis sp. strain SC2 to adapt to increased salinity. When exposed to 0.75% NaCl, methane oxidation was completely inhibited for 2.25 h and fully recovered within 6 h. Growth was inhibited for 23.5 h and then fully recovered. Its transcriptome was profiled after 0 min (control), 45 min (early response) and 14 h (late response) of stress exposure...
August 11, 2017: Applied and Environmental Microbiology
Suchawan Pornsukarom, Siddhartha Thakur
The aim of this study was to characterize the plasmids carrying antimicrobial resistance (AMR) determinants in multiple Salmonella serotypes recovered from the commercial swine farms environment after manure application on land. Manure and soil samples were collected on day0 before and after manure application on six farms in North Carolina and sequential soil samples were recollected on day7, 14, and 21 from the same plots. All environmental samples were processed for Salmonella and their plasmid contents were further characterized...
August 11, 2017: Applied and Environmental Microbiology
Hannah J Munro, Nicholas H Ogden, L Robbin Lindsay, Gregory J Robertson, Hugh Whitney, Andrew S Lang
The first report of members of the spirochete genus Borrelia in the seabird tick, Ixodes uriae, and seabird colonies occurred during the early 1990s. Since then, Borrelia spp. have been detected in these ticks and seabird colonies around the world. To-date, the primary species detected has been B. garinii, with rare occurrences of B. burgdorferi sensu stricto and B. lusitaniae. During our research on Borrelia and I. uriae in seabird colonies of Newfoundland and Labrador, Canada, we have identified B. bavariensis in I...
August 11, 2017: Applied and Environmental Microbiology
Brett M Barney, Mary H Plunkett, Velmurugan Natarajan, Florence Mus, Carolann M Knutson, John W Peters
Biological nitrogen fixation is accomplished by a diverse group of organisms known as diazotrophs, and requires the function of the complex metalloenzyme nitrogenase. Nitrogenase and many of the accessory proteins required for proper cofactor biosynthesis and incorporation into the enzyme have been characterized, but a complete picture of the reaction mechanism and key cellular changes that accompany biological nitrogen fixation remain to be fully elucidated. Studies have revealed that specific disruptions to the anti-activator encoding gene nifL result in the deregulation of the nif transcriptional activator NifA in the nitrogen-fixing bacterium Azotobacter vinelandii, triggering the production of extracellular ammonium levels approaching 30 mM during the stationary phase of growth...
August 11, 2017: Applied and Environmental Microbiology
Andrea Cossu, Yang Si, Gang Sun, Nitin Nitin
Bacterial biofilm formation is linked to several infections and foodborne disease outbreaks. To address this challenge, there is an unmet need to develop rechargeable antimicrobial materials that can provide continuous sanitation of contact surfaces especially in the food industry. This study was aimed at evaluating a novel rechargeable antimicrobial polymer formed using PVA-co-PE with halamine functionality to prevent biofilm formation with repeated exposure to high loads of bacteria and organic content and also aid in inactivation of pre-formed biofilms upon contact with this novel material...
August 11, 2017: Applied and Environmental Microbiology
Sabino Pacheco, Isabel Gómez, Jorge Sanchez, Blanca-Ines García-Gómez, Mario Soberón, Alejandra Bravo
Bacillus thuringiensis three domain Cry toxins kill insects by forming pores in the apical membrane of larval midgut cells. Oligomerization of the toxin is an important step for pore formation. Domain I helix α-3 participates in toxin oligomerization. Here we identify an intra-molecular salt bridge within helix α-3 of Cry4Ba (D111-K115) that is conserved in many members of the family of the three-domain Cry toxins. Single point mutations such as D111K or K115D resulted in proteins severely affected in toxicity...
August 11, 2017: Applied and Environmental Microbiology
Takumi Horiike, Yuma Dotsuta, Yuriko Nakano, Asumi Ochiai, Satoshi Utsunomiya, Toshihiko Ohnuki, Mitsuo Yamashita
Radioactive strontium ((90)Sr) leaked into saline environments, including the ocean, from the Fukushima Daiichi Nuclear Power Plant after a nuclear accident. Since the removal of (90)Sr using general adsorbents (e.g., zeolite) is not efficient at high salinity, a suitable alternative immobilization method is necessary. Therefore, we incorporated soluble Sr into biogenic carbonate minerals generated by urease-producing microorganisms from a saline solution. An isolate, Bacillus sp. strain TK2d, from marine sediment removed > 99% Sr after contact for four days in a saline solution (1...
August 11, 2017: Applied and Environmental Microbiology
Chen-Gao Wu, Jia-Long Tian, Rui Liu, Peng-Fei Cao, Tian-Jun Zhang, Ang Ren, Liang Shi, Ming-Wen Zhao
Putrescine is an important polyamine that participates in a variety of stress responses. Ornithine decarboxylase (ODC) is a key enzyme that catalyzes the biosynthesis of putrescine. A homolog of the gene encoding ODC was cloned from Ganoderma lucidum In the ODC-silenced strains, the transcript levels of the ODC gene and the putrescine content were significantly decreased. The ODC-silenced strains were more sensitive to oxidative stress. The content of ganoderic acid was increased by approximately 43-46% in the ODC-silenced strains...
August 11, 2017: Applied and Environmental Microbiology
Tom J Overbeck, Dennis L Welker, Joanne E Hughes, James L Steele, Jeff R Broadbent
This study explored transient inactivation of the gene encoding the DNA mismatch repair enzyme MutS as a tool for adaptive evolution of Lactobacillus casei MutS deletion derivatives of L. casei 12A and ATCC 334 were constructed and subject to a 100-day adaptive evolution process to increase lactic acid resistance at low pH. Wild-type parental strains were also subject to this treatment. At the end of the process, the ΔmutS lesion was repaired in representative L. casei 12A and ATCC 334 ΔmutS isolates. Growth studies in broth at pH 4...
August 11, 2017: Applied and Environmental Microbiology
Ryan Mercer, Oanh Nguyen, Qixing Ou, Lynn McMullen, Michael G Gänzle
The locus of heat resistance (LHR) is a 15 - 19 kb genomic island conferring exceptional heat resistance to organisms in the family Enterobacteriaceae including pathogenic strains of Salmonella enterica and Escherichia coli The complement of LHR-encoded genes that is necessary for heat resistance and the stress- or growth-phase induced expression of LHR-encoded genes are unknown. This study determined the contribution of the 7 LHR-encoded genes yfdX1GI, yfdX2, hdeDGI, orf11, trxGI, kefB, and psiEGI by comparison of the heat resistance of E...
August 11, 2017: Applied and Environmental Microbiology
Nathaniel A Losey, Florence Mus, John W Peters, Huynh M Le, Michael J McInerney
Syntrophomonas wolfei syntrophically oxidizes short-chain fatty acids (four to eight carbon in length) when grown in coculture with a hydrogen- and/or formate-using methanogen. The oxidation of 3-hydroxybutyryl-CoA, formed during butyrate metabolism, results in the production of NADH. The enzyme systems involved in NADH reoxidation in S. wolfei are not well understood. The genome of S. wolfei contains a multimeric [FeFe]-hydrogenase that may be a mechanism for NADH reoxidation. The S. wolfei genes for the multimeric [FeFe]-hydrogenase (hyd1ABC; SWOL_RS05165, SWOL_RS05170, SWOL_RS05175) and [FeFe]-hydrogenase maturation proteins (SWOL_RS05180, SWOL_RS05190, SWOL_RS01625) were co-expressed in Escherichia coli and the recombinant Hyd1ABC was purified and characterized...
August 11, 2017: Applied and Environmental Microbiology
Dai Komiya, Akane Hori, Takuya Ishida, Kiyohiko Igarashi, Masahiro Samejima, Takuya Koseki, Shinya Fushinobu
Acetyl xylan esterase (AXE) catalyzes the hydrolysis of the acetyl bonds present in plant cell wall polysaccharides. Here, we determined the crystal structure of AXE from Aspergillus luchuensis (AlAXEA), providing the three-dimensional structure of an enzyme in the Esterase_phb family. AlAXEA shares its core α/β-hydrolase fold structure with esterases in other families, but it has an extended central β-sheet at both its ends and an extra loop. Structural comparison with a ferulic acid esterase (FAE) from Aspergillus niger indicated that AlAXEA has conserved catalytic machinery: a catalytic triad (Ser119, His259, and Asp202) and an oxyanion hole (Cys40 and Ser120)...
August 11, 2017: Applied and Environmental Microbiology
Kuang He, Stuart A Gilder, William D Orsi, Xiangyu Zhao, Nikolai Petersen
Magnetotactic bacteria (MTB) swim along magnetic field lines in water. They are found in aquatic habitats throughout the world, yet knowledge of their spatial and temporal distribution remains limited. To help remedy this, we took MTB-bearing sediment from a natural pond, mixed the thoroughly homogenized sediment into two replicate aquaria, and then counted three dominant MTB morphotypes (cocci, spirilla and rod-shaped MTB cells) at high spatiotemporal sampling resolution: 36 discrete points in replicate aquaria were sampled every ∼30 days over 198 days...
August 4, 2017: Applied and Environmental Microbiology
N B Justice, A Sczesnak, T C Hazen, A P Arkin
A central goal of microbial ecology is to identify and quantify the forces that lead to observed population distributions and dynamics. However, these forces, which include environmental selection, dispersal, and organism interactions, are often difficult to assess in natural environments. Here, we present a method that links microbial community structures with selective and stochastic forces through highly replicated subsampling and enrichment of a single environmental inoculum. Specifically, groundwater from a well-studied natural aquifer was serially diluted and inoculated into nearly 1,000 aerobic and anaerobic nitrate-reducing cultures and final community structures evaluated with 16S rRNA gene amplicon sequencing...
August 4, 2017: Applied and Environmental Microbiology
Annette Summers Engel, Chang Liu, Audrey T Paterson, Laurie C Anderson, R Eugene Turner, Edward B Overton
Coastal salt marshes along the northern Gulf of Mexico shoreline received varied types and amounts of weathered oil residues after the 2010 Deepwater Horizon oil spill. At the time, predicting how marsh bacterial communities would respond and/or recover to oiling and other environmental stressors was difficult because baseline information on community composition and dynamics was generally unavailable. Here, we evaluated marsh vegetation, physicochemistry, flooding frequency, hydrocarbon chemistry, and subtidal sediment bacterial communities from 16S rRNA gene surveys at 11 sites in southern Louisiana before the oil spill, and resampled the same marshes three to four times over 38 months after the spill...
August 4, 2017: Applied and Environmental Microbiology
Peng Zhou, Xiaoli Li, I-Hsiu Huang, Fengxia Qi
The oral biofilm is a multispecies community in which antagonism and mutualism coexist amongst friends and foes to keep an ecological balance of community members. The pioneer colonizers such as Streptococcus gordonii produce H2O2 to inhibit the growth of competitors like the Mutans streptococci as well as strict anaerobic middle and later colonizers of the dental biofilm. Interestingly, the Veillonella species, as early colonizers, physically interact (coaggregate) with S. gordonii A putative catalase gene (catA) is found in most sequenced Veillonella species; however, the function of this gene is unknown...
August 4, 2017: Applied and Environmental Microbiology
Lowela Siarot, Hiroki Toyazaki, Makoto Hidaka, Keigo Kurumisawa, Tomoki Hirakawa, Kengo Morohashi, Toshihiro Aono
Bacteria have multiple K(+) uptake systems. Escherichia coli, for example, has three types of K(+) uptake systems, which include the low K(+)-inducible KdpFABC system and the two constitutive systems, the TrkAG/TrkAH and Kup systems. Azorhizobium caulinodans ORS571, a rhizobium that forms nitrogen-fixing nodules on the stems and roots of Sesbania rostrata, also has three types of K(+) uptake systems. Through phylogenetic analysis, we found that A. caulinodans has two trkG/H homologous genes, designated as trkI and trkJ...
August 4, 2017: Applied and Environmental Microbiology
Mikas Sadauskas, Justas Vaitekūnas, Renata Gasparavičiūtė, Rolandas Meškys
Indole is a molecule of considerable biochemical significance, acting as both an interspecies signal molecule and a building block of biological elements. Bacterial indole degradation has been demonstrated for a number of cases; however, very little is known about genes and proteins involved in this process. This study reports the cloning and initial functional characterization of genes (iif and ant cluster), responsible for indole biodegradation in Acinetobacter sp. strain O153. Catabolic cascade was reconstituted in vitro with recombinant proteins and each protein was assigned an enzymatic function...
August 4, 2017: Applied and Environmental Microbiology
J L McCarville, J Dong, A Caminero, M Bermudez-Brito, J Jury, J A Murray, S Duboux, M Steinmann, M Delley, M Tangyu, P Langella, A Mercenier, G Bergonzelli, E F Verdu
Microbiota-modulating strategies, including probiotic administration, have been tested for the treatment of chronic gastrointestinal diseases despite limited information regarding their mechanisms of action. We previously demonstrated that patients with active celiac disease have decreased duodenal expression of elafin, a human serine protease inhibitor, and supplementation of elafin by a recombinant Lactococcus lactis prevents gliadin-induced immunopathology in the NOD/DQ8 mouse model of gluten sensitivity...
August 4, 2017: Applied and Environmental Microbiology
Yuan Fang, Ryan G Mercer, Lynn M McMullen, Michael G Gänzle
The prophage-encoded Shiga toxin is a major virulence factor in Stx producing Escherichia coli (STEC). Toxin and phage production are linked, and occur after induction of the RecA-dependent SOS response. However, food-related stress and Stx prophage induction have not been studied on the single-cell level. This study investigated the effects of abiotic environmental stress on stx expression by single-cell quantification of gene expression in STEC O104:H4 Δstx2:gfp:amp(r). In addition, the effect of stress on production of phage particles was determined...
August 4, 2017: Applied and Environmental Microbiology
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