Spotlight
Biodegradation
Biodegradation | SpotlightMetabolites of an Oil Field Sulfide-Oxidizing, Nitrate-Reducing Sulfurimonas sp. Cause Severe CorrosionAmbiguous reports of corrosion problems associated with the injection of nitrate for souring control necessitate a deeper understanding of this frequently applied bioengineering strategy. Sulfide-oxidizing, nitrate-reducing bacteria have been proposed as key culprits, despite the underlying microbial corrosion mechanisms remaining insufficiently understood. This study provides a comprehensive characterization of how individual metabolic...
BiodegradationMetabolites Involved in Aerobic Degradation of the A and B Rings of EstrogenEstrogens, often detected in surface waters worldwide, have been classified as endocrine disrupting chemicals and carcinogens. Bacterial degradation is crucial for removing natural estrogens from natural and engineered ecosystems; however, current knowledge regarding the biochemical mechanisms and catabolic enzymes involved in estrogen biodegradation is very limited. Our estrogen metabolite profile and genomic analyses on estrone-...
Biotechnology
BiotechnologyForced Recycling of an AMA1-Based Genome-Editing Plasmid Allows for Efficient Multiple Gene Deletion/Integration in the Industrial Filamentous Fungus Aspergillus oryzaeMultiple gene modifications of specific fungal strains are required for achieving industrial-scale production of enzymes and secondary metabolites. In the present study, we developed an efficient multiple genetic engineering technique for the filamentous fungus Aspergillus oryzae. The approach is based on a clustered regulatory interspaced short palindromic repeats (...
BiotechnologyComparative Biochemical and Structural Analysis of Novel Cellulose Binding Proteins (Tāpirins) from Extremely Thermophilic Caldicellulosiruptor SpeciesThe mechanisms by which microorganisms attach to and degrade lignocellulose are important to understand if effective approaches for conversion of plant biomass into fuels and chemicals are to be developed. Caldicellulosiruptor species grow on carbohydrates from lignocellulose at elevated temperatures and have biotechnological significance for that reason. Novel cellulose binding proteins, called tāpirins, are involved in the...
Biotechnology | SpotlightRemedial Treatment of Corroded Iron Objects by Environmental Aeromonas IsolatesMicrobiology can greatly help in the quest for a sustainable solution to the problem of iron corrosion, which causes important economic losses in a wide range of fields, including the protection of cultural heritage and building materials. Using bacteria to transform reactive and unstable corrosion products into more-stable compounds represents a promising approach. The overall aim of this study was to develop a method for the...
Biotechnology | SpotlightThermal Stability of a Mercuric Reductase from the Red Sea Atlantis II Hot Brine Environment as Analyzed by Site-Directed MutagenesisThe Red Sea is an attractive environment for bioprospecting. There are 25 brine-filled deeps in the Red Sea. The Atlantis II brine pool is the biggest and hottest of such hydrothermal ecosystems. We generated an environmental mercuric reductase library from the lowermost layer of the Atlantis II brine pool, in which we identified two variants of the mercuric reductase enzyme (MerA). One is the previously described halophilic and...
Environmental Microbiology
Environmental MicrobiologyResponse of the Biocontrol Agent Pseudomonas pseudoalcaligenes AVO110 to Rosellinia necatrix ExudateDiseases associated with fungal root invasion cause a significant loss of fruit tree production worldwide. The bacterium Pseudomonas pseudoalcaligenes AVO110 controls avocado white root rot disease caused by Rosellinia necatrix by using mechanisms involving competition for nutrients and niches. Here...
Environmental Microbiology | SpotlightNovel Cholera Toxin Variant and ToxT Regulon in Environmental Vibrio mimicus Isolates: Potential Resources for the Evolution of Vibrio cholerae Hybrid StrainsNatural diversification of CTXФ and ctxAB genes certainly influences disease severity and shifting patterns in major etiological agents of cholera, e.g., the overwhelming emergence of hybrid El Tor variants, replacing the prototype El Tor strains of V. cholerae. This report, showing the occurrence of CTXET comprising a novel variant of ctxAB...
Environmental MicrobiologyAntiparasitic Effect of Copper Alloy Surface on Cryptocaryon irritans in Aquaculture of Larimichthys croceaCryptocaryon irritans, a parasitic ciliate that penetrates the epithelium of the gills, skin, and fins of marine fish, causes acute suffocation and death in cultured fish within days of infection. Much of the existing research centers around the prevention of C. irritans infection, but no cure has...
Environmental MicrobiologyButyrivibrio hungatei MB2003 Competes Effectively for Soluble Sugars Released by Butyrivibrio proteoclasticus B316T during Growth on Xylan or PectinFeeding a future global population of 9 billion people and climate change are the primary challenges facing agriculture today. Ruminant livestock are important food-producing animals, and maximizing their productivity requires an understanding of their digestive systems and the roles played by rumen microbes in plant polysaccharide degradation. Butyrivibrio species are a phylogenetically diverse group of bacteria and are...
Environmental MicrobiologyPeriodic and Spatial Spreading of Alkanes and Alcanivorax Bacteria in Deep Waters of the Mariana TrenchIn the oligotrophic environment of the Mariana Trench, alkanes as carbohydrates are important for the ecosystem, but their spatial and periodic spreading in deep waters has never been reported. Alkane-degrading bacteria such as Alcanivorax spp. are biological signals of the alkane distribution. In the present study, Alcanivorax was abundant in some waters, at depths of up to 6,000 m, in the Mariana Trench. Genomic,...
Environmental MicrobiologypahE, a Functional Marker Gene for Polycyclic Aromatic Hydrocarbon-Degrading BacteriaPAH contamination has become a worldwide environmental issue because of the potential toxic effects on natural ecosystems and human health. Biotransformation and biodegradation are considered the main natural elimination forms of PAHs from contaminated sites. Therefore, the knowledge of the degradation potential of the microbial community in contaminated sites is crucial for PAH pollution bioremediation. However, the nonspecificity of...
Environmental MicrobiologyIron Homeostasis in Bacillus subtilis Requires Siderophore Production and Biofilm FormationIron acquisition is of fundamental importance for microorganisms, since this metal is generally poorly bioavailable under natural conditions. In the environment, most bacteria are found tightly packed within multicellular communities named biofilms. Here, using the soil Gram-positive bacterium Bacillus subtilis, we show that biofilm formation and the production of...
Environmental MicrobiologyRoles of d-Lactate Dehydrogenases in the Anaerobic Growth of Shewanella oneidensis MR-1 on SugarsNADH-dependent LDHs are conserved among diverse organisms and contribute to NAD+ regeneration in lactic acid fermentation. However, this type of LDH is also present in nonfermentative bacteria, including members of the genus Shewanella, while their physiological roles in these bacteria remain unknown. Here, we show that LdhA (an NADH-dependent...
Food Microbiology
Food MicrobiologyRNA Sequencing-Based Transcriptional Overview of Xerotolerance in Cronobacter sakazakii SP291Cronobacter sakazakii is a pathogen of importance to neonatal health and is known to persist in dry food matrices, such as powdered infant formula (PIF) and its associated production environment. When infections are reported in neonates, mortality rates can be high. The success of this bacterium in surviving these low-moisture environments suggests that...
Food MicrobiologyThe MarR Family Regulator BmrR Is Involved in Bile Tolerance of Bifidobacterium longum BBMN68 via Controlling the Expression of an ABC TransporterBifidobacteria are natural inhabitants of the human intestinal tract. Some bifidobacterial strains are used as probiotics in fermented dairy production because of their health-promoting effects. Following consumption, bifidobacteria colonize the lower intestinal tract, where the concentrations of bile salts remain nearly 0.05% to 2.0%. Bile salts, as detergent-like antimicrobial compounds, can cause cellular membrane disruption, protein...
Genetics and Molecular Biology
Genetics and Molecular BiologyNitric Oxide and Iron Signaling Cues Have Opposing Effects on Biofilm Development in Pseudomonas aeruginosaNitric oxide (NO), which induces biofilm dispersal, is a promising strategy for biofilm control in both clinical and industrial contexts. However, competing environmental signals may reduce the efficacy of NO. The results presented here suggest that the presence of iron represents one such environmental cue that antagonizes the activity of NO as a biofilm-dispersing agent. Based on this understanding, we developed a strategy to enhance...
Geomicrobiology
GeomicrobiologyMetal Reduction and Protein Secretion Genes Required for Iodate Reduction by Shewanella oneidensisMicrobial iodate (IO3−) reduction is a major component in the biogeochemical cycling of iodine and the bioremediation of iodine-contaminated environments; however, the molecular mechanism of microbial IO3− reduction is poorly understood. Results of the present study indicate that outer membrane (type II) protein secretion and metal reduction genes encoding the outer membrane MtrAB module of...
Methods
MethodsGeneration of Markerless Deletions in the Nosocomial Pathogen Clostridium difficile by Induction of DNA Double-Strand BreaksMost sequenced bacterial genomes contain genes encoding proteins of unknown or hypothetical function. To identify a phenotype for mutations in such genes, deletion is the preferred method for mutagenesis because it reduces the likelihood of polar effects, although it does not eliminate the possibility. Allelic exchange to produce deletions is dependent on the length of homologous regions used to generate merodiploids. Shorter regions of...
MethodsNoninvasive Detection of Equid Herpesviruses in Fecal SamplesEquid herpesviruses (EHVs) establish latent infections, and many EHVs are shed and transmitted via nasal discharge primarily through droplet and aerosol infection. Obtaining nasal swabs and other invasive samples from wildlife is often not possible without capture and physical restraint of individuals, which are resource intensive and a health risk for the captured animals. Fecal EHV shedding has never been demonstrated for naturally...
Microbial Ecology
Microbial EcologyFeeding Rapidly Alters Microbiome Composition and Gene Transcription in the Clownfish GutDespite extensive study of intestinal microbiome diversity and the role of diet type in structuring gut microbial communities, we know very little about short-term changes in the intestinal microbiome as a result of feeding alone. Sampling microbiomes over a feeding cycle will allow us to differentiate opportunistic, feeding-responsive microbes from resident, potentially commensal members of the gut community. Also, since feeding has...
Physiology
Physiology | SpotlightDiversity in CO2-Concentrating Mechanisms among Chemolithoautotrophs from the Genera Hydrogenovibrio, Thiomicrorhabdus, and Thiomicrospira, Ubiquitous in Sulfidic Habitats WorldwideAutotrophic organisms take up and fix DIC, introducing carbon into the biological portion of the global carbon cycle. The mechanisms for DIC uptake and fixation by autotrophic Bacteria and Archaea are likely to be diverse but have been well characterized only for “Cyanobacteria.” Based on genome sequences, members of the genera Hydrogenovibrio, Thiomicrospira, and Thiomicrorhabdus...
Public and Environmental Health Microbiology
Public and Environmental Health Microbiology1,4,7-Triazacyclononane Restores the Activity of β-Lactam Antibiotics against Metallo-β-Lactamase-Producing Enterobacteriaceae: Exploration of Potential Metallo-β-Lactamase InhibitorsCarbapenem-resistant Enterobacteriaceae (CRE)-mediated infections remain a significant public health concern and have been reported to be critical in the World Health Organization’s priority pathogens list for the research and development of new antibiotics. CRE produce enzymes, such as metallo-β-lactamases (MBLs), which inactivate β-lactam antibiotics. Combination therapies involving a β-lactam antibiotic and a β-lactamase...
Letter to the Editor
Letter to the EditorTowards a Genome-Based Reclassification of the Genus Lactobacillus
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Applied and Environmental Microbiology® (AEM) publishes study results that make significant contributions to applied microbial research, basic microbial ecology research, and genetic and molecular investigations of microbial topics of practical value.
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