PubMed Journal Database | Applied and environmental microbiology 
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Showing PubMed Articles 1–25 of 215 from Applied and environmental microbiology
Articles of significant interest selected from this issue by the editors.
A total of 214 rainwater samples from 82 tanks were collected in urban Southeast Queensland (SEQ) in Australia and analysed for the presence and numbers of zoonotic bacterial and protozoa pathogens using binary PCR and quantitative PCR (qPCR). Quantitative Microbial Risk Assessment (QMRA) analysis was used to quantify the risk of infection associated with the exposure to potential pathogens from potable and non-potable uses of roof-harvested rainwater. Of the 214 samples tested, 10.7%, 9.8%, 5.6%, and 0.4%...
We have developed a sensitive and highly efficient whole-cell methodology for quantitative analysis and screening of protease activity in vivo. The method is based on the ability of a genetically encoded protease to rescue a coexpressed short-lived fluorescent substrate reporter from cytoplasmic degradation, and thereby confer increased whole-cell fluorescence in proportion to the protease's apparent activity in the E. coli cytoplasm. We demonstrated that this system can reveal differences in the efficiency...
Medium chain fatty acids (octanoic and decanoic acid) are well known as fermentation inhibitors. During must fermentation the toxicity of these fatty acids is enhanced by ethanol and low pH, which favors their entrance in the cell, resulting in a decrease of internal pH. We present here the characterization of the mechanisms involved in the establishment of the resistance to these fatty acids. The analysis of the transcriptome response to the exposure to octanoic- and decanoic acid revealed that two partial...
A lacZ reporter system for use in Borrelia burgdorferi.
Regulation of gene expression is critical for the ability of Borrelia burgdorferi to adapt to different environments during its natural infectious cycle. Reporter genes have been used successfully to study gene regulation in multiple organisms. We have introduced a lacZ gene into B. burgdorferi and show that B. burgdorferi produces a protein with detectable β-galactosidase activity in both liquid and solid media when lacZ is expressed from a constitutive promoter. Furthermore, when lacZ is expressed from t...
Schwanniomyces occidentalis β-fructofuranosidase (Ffase) releases β-fructose from the non-reducing end of β-fructans and synthesizes 6-kestose and 1-kestose, both considered as prebiotic fructooligosaccharides. Analysing the amino acid sequence of this protein reveals that it includes a serine instead of a leucine at position 196, caused by a non-universal decoding of the unique mRNA leucine codon CUG. Substitution of Ser196 by leucine dramatically lowers the apparent catalytic efficiency (kcat/Km) of th...
Soil bacterial composition co-varies with plant rarity.
Rare and common plants are predicted to host different rhizospheric microbes. To evaluate this prediction, we used T-RFLP to compare rhizospheric bacteria from eight native grass species spanning a 15-fold range in local abundance in their natural ecosystem. We observed that locally rare versus common plants associated with divergent bacterial communities.
The recent increased detection of acetic acid bacteria of the genus Asaia as symbionts of mosquitoes, such as Anopheles spp. and Aedes spp., prompted us to investigate the diversity of these symbionts and their relationships in different mosquito species and populations. Following cultivation-dependent and -independent techniques, we investigated the microbiota associated with four mosquito species, Anopheles stephensi, Anopheles gambiae, Aedes aegypti and Aedes albopictus, which are important vectors of hu...
Stable site-specific fluorescent tagging constructs optimized for Burkholderia species.
Several vectors were constructed that facilitate stable fluorescent labeling of Burkholderia pseudomallei and Burkholderia thailandensis. These vectors combined the effectiveness of the miniTn7 site-specific transposition system with fluorescent proteins optimized for Burkholderia spp., enabling bacterial tracking during cellular infection.
Mealybugs (Coccoidea: Pseudococcidae) are sap-sucking plant parasites that harbor bacterial endosymbionts within specialized organs. Previous studies have identified two subfamilies, Pseudococcinae and Phenacoccinae, within mealybugs, and determined the primary endosymbionts (P-endosymbionts) of the Pseudococcinae to be β Proteobacteria (Candidatus Tremblaya princeps) containing γ Proteobacteria secondary symbionts. Here the P-endosymbionts of phenacoccine mealybugs are characterized based on 16S rRNA fro...
GRANULE FORMATION MECHANISMS WITHIN AN AEROBIC WASTEWATER SYSTEM OPERATING FOR PHOSPHORUS REMOVAL.
Granular sludge is a novel alternative for the treatment of wastewater and offers numerous operational and economic advantages compared with conventional floccular sludge systems. The majority of research on granular sludge has focused on optimisation of engineering aspects relating to reactor operation with little emphasis on the fundamental microbiology. In this study we hypothesise two novel mechanisms for granule formation as observed in three laboratory-scale sequencing batch reactors operating for bio...
The effect of exposure to acid (pH 2.5), alkaline (pH 11.0), heat (55°-C) and oxidative (40 mM H2O2) lethal conditions on the ultrastructure and global chemical composition of Salmonella enterica serovar Typhimurium CECT 443 cells was studied using transmission electron microscopy and Fourier Transform Infrared spectroscopy (FT-IR) combined with multivariate statistical methods (Hierarchical Cluster Analysis and Factor Analysis). Infrared spectra exhibited marked differences in the five spectral regions, f...
Rumen Microbial Population Dynamics during Adaptation to a High Grain Diet.
High grain adaptation programs are widely used in feedlot cattle to balance enhanced growth performance against the risk of acidosis. This adaptation to a high grain diet from a high forage diet is known to change the rumen microbial population structure and help establish a stable microbial population within the rumen. Therefore, to evaluate bacterial population dynamics during adaptation to a high grain diet, 4 ruminally canulated beef steers were adapted to high grain diet using a step-up diet regime con...
In order to introduce specificity for Mycobacterium avium subsp. paratuberculosis prior to a phage amplification assay, various magnetic separation approaches, involving either antibodies or peptides, were evaluated in terms of capture efficiency (%) of M. avium subsp. paratuberculosis cells and % non-specific binding by other Mycobacterium spp. A 50:50 mix of MyOne(TM) Tosylactivated Dynabeads® coated with chemically synthesized biotinylated aMp3 and biotinylated aMptD M. avium subsp. paratuberculosis-spe...
Functionality of sortase A in Lactococcus lactis.
Lactococcus lactis IL1403 harbors a putative sortase A (SrtA) and 11 putative sortase substrates that carry the canonical LPXTG signature of such substrates. We report here on the functionality of SrtA to anchor 5 LPXTG substrates to the cell wall thus suggesting that SrtA is the housekeeping sortase in L. lactis IL1403.
Generally, prokaryotes store carbon as polyhydroxyalkanoate, starch, or glycogen. The Gram-positive Actinomycete Rhodococcus opacus strain PD630 is noteworthy in that it stores carbon in the form of triacylglycerides (TAGs). Several studies have demonstrated that R. opacus PD630 can accumulate up to 76% of its cell dry weight as TAGs when grown under nitrogen limiting conditions. While this process is well studied, the underlying molecular and biochemical mechanisms leading to TAG biosynthesis and subsequen...
The purpose of this study was to determine the occurrence, and genotypic relatedness of Salmonella isolates from feed and fecal samples in commercial swine production units. Of 275 feed samples, Salmonella was detected from 10 feed samples that originated from eight of 36 (22.2%) barns, with prevalence of 3.6% (10/275). In fecal samples, prevalence of 17.6% were found at early finishing stage (1180/6,880) with a significant reduction (7.4%) when pigs reached at market age (392/5,321). Of the 280 Salmonella...
Persistence of Bacteroides spp. populations in a river measured by molecular and culture techniques.
Given the interest in Bacteroides as a microbial source tracking (MST) marker, and the limited knowledge of their survival in the environment, here we examine the survival of Bact. fragilis, Bact. thetaiotaomicron and environmental species of Bacteroides using culture techniques and molecular tools. Two kinds of experiments were performed: (i) on site experiments, in which bacteria were exposed to changes in several environmental parameters in a river; and (ii) microcosm assays in the laboratory, with contr...
We describe a genetic system for producing specific gene knockouts in Cyanothece sp. Strain PCC 7822 using a ssDNA technique (37). The first fully segregated mutant was in the nifK gene (ΔnifK) and the mutant was unable to grow on a medium lacking combined nitrogen and produced virtually no hydrogen.
Global atmospheric carbon dioxide (CO2) concentration is expected to increase continuously over the next century. However, little is known about the responses of soil bacterial communities to elevated CO2 in terrestrial ecosystems. This study aimed to partition the relative influence of CO2, nitrogen (N) and spatial factor (different sampling plots) on soil bacterial communities at the free air CO2 enrichment research site in Duke Forest, USA by two independent techniques of entirely sequencing-based approa...
Fusobacterium nucleatum is a periodontal pathogen that has been directly associated with the development and progression of periodontal disease, a widespread pathology that affects the support tissues of the tooth. We isolated a new bacteriophage (FnpΦ02) that specifically infects this bacterium. Transmission electron microscopy showed that the virion is composed of an icosahedral head and a segmented tail. The size of the phage genome was estimated to be approximately 59 kbp of double-stranded DNA. The mo...
Industrial penicillin production levels by the filamentous fungus Penicillium chrysogenum increased dramatically by classical strain improvement. High yielding strains contain multiple copies of the penicillin biosynthetic gene cluster that encodes the three key enzymes of β-lactam biosynthetic pathway. We have analyzed the gene cluster dose effect on penicillin production using the high yielding P. chrysogenum strain DS17690 that was cured from its native clusters. The amount of penicillin V produced incr...
The 37 kDa Oncofetal antigen (OFA), a tumor immunogen expressed on all mammalian cancers examined to date, was secreted and anchored to the cell wall of L. plantarum using homologous signal peptides and LPxTG-anchors. Orally administrated L. plantarum expressing anchored OFA induced a specific immune response against OFA in mice.
Low and Medium Pressure UV Inactivation of Adenoviruses: The Effect of Host Cells.
Ultraviolet (UV) disinfection is highly effective against most pathogens, with the exception of the adenoviruses (AD). To date, many studies have focused on low pressure (LP) UV inactivation of AD but little is known about the effect of medium pressure (MP) UV. Despite numerous studies on LP UV inactivation of AD, extreme variabilities in AD's LP UV dose requirements had been observed because of differing experimental conditions such as the types of cell lines used for AD enumeration. This study therefore i...
