Spotlight
Biodegradation
BiodegradationCopper in Wood Preservatives Delayed Wood Decomposition and Shifted Soil Fungal but Not Bacterial Community CompositionCopper-containing rather than TRIQAC formulations are efficient wood preservatives irrespective of the origin and composition of the soil microbial communities. However, some fungi appear to be naturally insensitive to copper and should be the focus of future wood preservative formulations to facilitate the life span of wooden construction in contact with soil while also minimizing the overall environmental impact.
Biotechnology
BiotechnologyDiscovery of 16-Demethylrifamycins by Removing the Predominant Polyketide Biosynthesis Pathway in Micromonospora sp. Strain TP-A0468Natural products are essential in the development of novel clinically used drugs. Discovering new natural products and modifying known compounds are still the two main ways to generate new candidates. Here, we have discovered several rifamycins with varied skeleton structures by redirecting the metabolic flux from the predominant polyketide biosynthetic pathway to the rifamycin pathway in the marine actinomycetes species ...
Environmental Microbiology
Environmental MicrobiologyMolecular Adaptations of Bacterial Mercuric Reductase to the Hypersaline Kebrit Deep in the Red SeaAnalysis of two structurally homologous but catalytically distinct mercuric reductases from the Kebrit Deep brine in the Red Sea sheds light on the adaptations that enable microorganisms to cope simultaneously with extreme salinity and toxic mercury compounds. One is strongly inhibited by high NaCl concentrations, while the other exhibits NaCl-dependent activation. Their different activity profiles imply that they may derive from...
Environmental MicrobiologyThe Ferredoxin-Like Protein FerR Regulates PrbP Activity in Liberibacter asiaticusThe rapid spread and aggressive progression of huanglongbing (HLB) in the major citrus-producing areas have raised global recognition of and vigilance to this disease. As a result, the causative agent, Liberibacter asiaticus, has been investigated from various perspectives. However, gene expression regulatory mechanisms that are important for the survival and...
Environmental MicrobiologyTwo-Stage Cultivation of Dunaliella tertiolecta with Glycerol and Triethylamine for Lipid Accumulation: a Viable Way To Alleviate the Inhibitory Effect of Triethylamine on BiomassMicroalgae are promising alternatives for sustainable biodiesel production. Two-stage cultivation with glycerol and triethylamine enhanced the lipid productivity of Dunaliella tertiolecta, indicating that two-stage cultivation is an efficient strategy for biodiesel production from microalgae. It was found that glycerol significantly enhanced cell biomass of...
Evolutionary and Genomic Microbiology
Evolutionary and Genomic MicrobiologyRapid Parallel Evolution of Azole Fungicide Resistance in Australian Populations of the Wheat Pathogen Zymoseptoria triticiFungicides are essential to control diseases in agriculture because many crops are highly susceptible to pathogens. However, many pathogens rapidly evolve resistance to fungicides. A large body of studies have described specific mutations conferring resistance and have often made inferences about the origins of resistance based on sequencing data from the target gene alone. Here, we show the de novo acquisition of resistance to...
Evolutionary and Genomic Microbiology | SpotlightResistance Gene Carriage Predicts Growth of Natural and Clinical Escherichia coli Isolates in the Absence of AntibioticsManaging the spread of antibiotic resistance in bacterial pathogens is a major challenge for global public health. Central to this challenge is understanding whether resistance is linked to impaired bacterial growth in the absence of antibiotics, because this determines whether resistance declines when bacteria are no longer exposed to antibiotics. We studied 92 isolates of the key bacterial pathogen...
Food Microbiology
Food MicrobiologyBrettanomyces bruxellensis SSU1 Haplotypes Confer Different Levels of Sulfite Tolerance When Expressed in a Saccharomyces cerevisiae SSU1 Null MutantBrettanomyces bruxellensis is one of the most important wine spoilage microorganisms, with the use of sulfite being the major method to control spoilage. However, this species displays a wide intraspecies distribution in sulfite tolerance, with some strains capable of tolerating high concentrations of SO2, with relatively high concentrations of this...
Food MicrobiologyA Combination of Linalool, Vitamin C, and Copper Synergistically Triggers Reactive Oxygen Species and DNA Damage and Inhibits Salmonella enterica subsp. enterica Serovar Typhi and Vibrio fluvialisThere is a need to develop effective antibacterial therapies for mitigating bacterial pathogens in food systems. We used a 3D checkerboard assay to ascertain a safe synergistic combination of food-grade components: vitamin C, copper, and the essential oil linalool. Individually, these constituents have to be added in large amounts to exert their antibacterial effect, which leads to unwanted organoleptic properties. The triple...
Genetics and Molecular Biology
Genetics and Molecular Biology | SpotlightAcrR and Rex Control Mannitol and Sorbitol Utilization through Their Cross-Regulation of Aldehyde-Alcohol Dehydrogenase (AdhE) in Lactobacillus plantarumThe function and regulation of AdhE in the important probiotic genus Lactobacillus are rarely reported. Here we demonstrated that AdhE is responsible for sorbitol and mannitol utilization and is cross-regulated by two transcriptional regulators in L. plantarum NF92, which had not been reported previously. This is important for...
Genetics and Molecular BiologyNovel Two-Component System MacRS Is a Pleiotropic Regulator That Controls Multiple Morphogenic Membrane Protein Genes in Streptomyces coelicolorTCSs help bacteria adapt to environmental stresses by altering gene expression. However, the roles and corresponding regulatory mechanisms of most TCSs in the Streptomyces model strain S. coelicolor are unknown. We investigated the previously uncharacterized MacRS TCS and identified the core DNA recognition sequence, two seven-nucleotide inverted repeats, for...
Genetics and Molecular Biology | SpotlightInduction of a Toxin-Antitoxin Gene Cassette under High Hydrostatic Pressure Enables Markerless Gene Disruption in the Hyperthermophilic Archaeon Pyrococcus yayanosiiGenetic manipulations in hyperthermophiles have been studied for over 20 years. However, the extremely high temperatures under which these organisms grow have limited the development of genetic tools. In this study, an HHP-inducible promoter was used to control the expression of a toxin. Compared to sugar-inducible and cold-shock-inducible promoters, the HHP-inducible promoter rarely has negative effects on the overall physiology and...
Genetics and Molecular BiologyAlternative Biosynthetic Starter Units Enhance the Structural Diversity of Cyanobacterial LipopeptidesHerein, we deciphered the most important biosynthetic traits of a prominent group of bioactive lipopeptides. We reveal evidence for initiation of biosynthesis by two alternative starter units hardwired directly in the same gene cluster, eventually resulting in the production of a remarkable range of lipopeptide variants. We identified several unusual tailoring genes potentially involved in modifying the fatty acid chain. Careful...
Invertebrate Microbiology
Invertebrate Microbiology | SpotlightTwo Photolyases Repair Distinct DNA Lesions and Reactivate UVB-Inactivated Conidia of an Insect Mycopathogen under Visible LightProtecting fungal cells from damage from solar UVB irradiation is critical for development and application of fungal insecticides but is mechanistically not understood in Beauveria bassiana, a classic insect pathogen. We unveil that two intranuclear photolyases, Phr1 and Phr2, play essential roles in repairing UVB-induced dsDNA lesions through respective decomposition...
Microbial Ecology
Microbial EcologyMicrobial Organic Matter Degradation Potential in Baltic Sea Sediments Is Influenced by Depositional Conditions and In Situ GeochemistrySediments sequester organic matter over geologic time scales and impact global climate regulation. Microbial communities in marine sediments drive organic matter degradation, but the factors controlling their assemblages and activities, which in turn impact their role in organic matter degradation, are not well understood. Hence, determining the role of microbial communities in carbon cycling in various sediment types is necessary for...
Microbial Ecology | SpotlightChanges in the Rumen Microbiota of Cows in Response to Dietary Supplementation with Nitrate, Linseed, and Saponin Alone or in CombinationThis study aimed at identifying the microbial mechanisms of enteric methane mitigation when linseed, nitrate, and saponins were fed to nonlactating cows alone or in a combination. Hydrogen is a limiting factor in rumen methanogenesis. We hypothesized that linseed and saponins would affect hydrogen producers and nitrate would affect hydrogen consumption, leading to reduced methane production in the rumen. Contrary to what was predicted,...
Physiology
PhysiologyGalactose Impacts the Size and Intracellular Composition of the Asaccharolytic Oral Pathobiont Porphyromonas gingivalisEnvironmental perturbations are central to the ability of pathobionts, such as Porphyromonas gingivalis, to promote the development of diseased sites. In the case of periodontal disease, increased local pH, a shift to anaerobic surroundings, and the accumulation of Gram-negative anaerobes at the expense of Gram-positive cocci are known ecological fluctuations...
Public and Environmental Health Microbiology
Public and Environmental Health MicrobiologyChlortetracycline Enhances Tonsil Colonization and Fecal Shedding of Multidrug-Resistant Salmonella enterica Serovar Typhimurium DT104 without Major Alterations to the Porcine Tonsillar and Intestinal MicrobiotaSalmonella spp. are an important cause of foodborne illness in North America, and pork products are associated with sporadic cases and outbreaks of human salmonellosis. Isolates of Salmonella may be resistant to multiple antibiotics, and infections with multidrug-resistant (MDR) Salmonella spp. are more difficult to treat, leading to increased...
Public and Environmental Health MicrobiologyPopulation Genetics and Characterization of Campylobacter jejuni Isolates from Western Jackdaws and Game Birds in FinlandThe roles of environmental reservoirs, including wild birds, in the molecular epidemiology of Campylobacter jejuni have not been assessed in depth. Our results showed that game birds may pose a risk for acquiring campylobacteriosis, because they had C. jejuni genomotypes highly similar to human...
Public and Environmental Health Microbiology | SpotlightLoss of Function in Escherichia coli Exposed to Environmentally Relevant Concentrations of Benzalkonium ChlorideExposure to very low concentrations of biocides in the environment is a poorly understood risk factor for antimicrobial resistance. Repeated exposure to trace levels of the biocide benzalkonium chloride (BAC) resulted in loss of function (motility) and a general reduction in bacterial fitness but relatively minor decreases in susceptibility. These changes were accompanied by widespread changes in the...
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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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Dr. Harold L. Drake, Editor in Chief