Cometabolic biodegradation of quizalofop-p-ethyl by Methylobacterium populi YC-XJ1 and identification of QPEH1 esterase

BACKGROUND: Quizalofop-p-ethyl (QPE), a unitary R configuration aromatic oxyphenoxypropionic acid ester (AOPP) herbicide, was widely used and had led to detrimental environmental effects. For finding the QPEdegrading bacteria and promoting the biodegradation of QPE, a series of studies were carried out. RESULTS: A QPE-degrading bacterial strain YC-XJ1 was isolated from desert soil and identified as Methylobacterium populi, which could degrade QPE with methanol by cometabolism. Ninety-seven percent of QPE (50 mg/L) could be degraded within 72 h under optimum biodegradation condition of 35°C and pH 8.0. The maximum degradation rate of QPE was 1.4 mg/L/h, and the strain YC-XJ1 exhibited some certain salinity tolerance. Two novel metabolites, 2-hydroxy-6-chloroquinoxaline and quinoxaline, were found by high-performance liquid chromatography/mass spectroscopy analysis. The metabolic pathway of QPE was predicted. The catalytic efficiency of strain YC-XJ1 toward different AOPPs herbicides in descending order was as follows: haloxyfop-pmethyl ≈ diclofop-methyl ≈ fluazifop-p-butyl N clodinafop-propargyl N cyhalofop-butyl N quizalofop-p-ethyl N fenoxaprop-p-ethyl N propaquizafop N quizalofop-p-tefuryl. The genome of strain YC-XJ1 was sequenced using a combination of PacBio RS II and Illumina platforms. According to the annotation result, one α/ß hydrolase gene was selected and named qpeh1, for which QPE-degrading function has obtained validation. Based on the phylogenetic analysis and multiple sequence alignment with other QPE-degrading esterases reported previously, the QPEH1 was clustered with esterase family V. CONCLUSION: M. populi YC-XJ1 could degrade QPE with a novel pathway, and the qpeh1 gene was identified as one of QPE-degrading esterase gene.

Adhesion and Biofilm Formation Abilities of Bacteria Isolated from Dental Unit Waterlines / 치위생과학회지

The purpose of our study is to compare the adhesion and biofilm formation abilities of isolates from water discharged from dental unit waterlines (DUWLs). Bacteria were isolated from a total of 15 DUWLs. Twelve isolates were selected for the experiment. To confirm the adhesion ability of the isolates, each isolate was attached to a glass coverslip using a 12-well plate. Plates were incubated at 26℃ for 7 days, and the degree of adhesion of each isolate was scored. To verify the biofilm formation ability of each isolate, biofilms were allowed to form on a 96-well polystyrene flat-bottom microtiter plate. The biofilm accumulations of all isolates formed at 26℃ for 7 days were identified and compared. A total of 56 strains were isolated from 15 water samples including 12 genera and 31 species. Of the 56 isolates, 12 isolates were selected according to the genus and used in the experiment. Sphingomonas echinoides, Methylobacterium aquaticum, and Cupriavidus pauculus had the highest adhesion ability scores of +3 among 12 isolates. Among these three isolates, the biofilm accumulation of C. pauculus was the highest and that of S. echinoides was the third-most abundant. The lowest biofilm accumulations were identified in Microbacterium testaceum and M. aquaticum. Most isolates with high adhesion ability also exhibited high biofilm formation ability. Analysis of adhesion and biofilm formation of the isolates from DUWLs can provide useful information to understand the mechanism of DUWL biofilm formation and development.

Influence of Chemical- and Natural-Based Lotions on Bacterial Communities in Human Forearm Skin

Purpose of this study was to evaluate the influence of a lotion on the bacterial community in the human forearm skin. The chemical- and natural-based lotions were applied on the left and right inner forearm skins, respectively, of 14 participants, who cleansed forearm skin using sterilized cotton swabs. The germs on cotton swabs were analyzed using libraries of PCR amplicons. The genetic diversity of the bacterial communities detected on the natural-based lotion-applied skin (NLS) was significantly higher than that of the bacterial communities on the chemical-based lotion-applied skin (CLS) in all participants, except two. The diversity was estimated based on operational taxonomic unit (OTU), Chao1, Shannon, and Simpson indices. Bacterial communities obtained from the CLS and NLS were phylogenetically separated into 5 and 3 monophyletic groups, respectively, based on lotion types. The taxonomic distribution of the bacterial communities, which were composed of 198 genera in 14 phyla in the CLS and NLS, respectively, was irregularly and biasedly separated into 2 groups based on the lotion types. Among the 14 phyla, Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria were found to be relatively dominant, and 15 of the 198 genera, including Methylobacterium, Propionibacterium, Pseudomonas, Staphylococcus, Streptococcus, and Bacillus were relatively dominant (>0.5%). The taxonomic distribution of dominant bacterial communities from CLS and NLS was irregularly and biasedly separated without relation to the lotion types. In conclusion, the chemical- and natural-based lotions were responsible for changing or influencing the genetic diversity, phylogenetic separation, and taxonomic distribution of skin bacterial communities.

First Case of Psychrobacter sanguinis Bacteremia in a Korean Patient / 대한임상미생물학회지

Psychrobacter sanguinis has been described as a Gram-negative, aerobic coccobacilli originally isolated from environments and seaweed samples. To date, 6 cases of P. sanguinis infection have been reported. A 53-year-old male was admitted with a generalized tonic seizure lasting for 1 minute with loss of consciousness and a mild fever of 37.8℃. A Gram stain revealed Gram-negative, small, and coccobacilli-shaped bacteria on blood culture. Automated microbiology analyzer identification using the BD BACTEC FX (BD Diagnostics, Germany) and VITEK2 (bioMérieux, France) systems indicated the presence of Methylobacterium spp., Aeromonas salmonicida, and the Moraxella group with low discrimination. The GenBank Basic Local Alignment Search Tool and an Ez-Taxon database search revealed that the 16S rRNA gene sequence of the isolate showed 99.30% and 99.88% homology to 859 base-pairs of the corresponding sequences of P. sanguinis, respectively (GenBank accession numbers JX501674.1 and HM212667.1). To the best of our knowledge, this is the first human case of P. sanguinis bacteremia in Korea. It is notable that we identified a case based on blood specimens that previously had been misidentified by a commercially automated identification analyzer. We utilized 16S rRNA gene sequencing as a secondary method for correctly identifying this microorganism.

Methylobacterium-plant interaction genes regulated by plant exudate and quorum sensing molecules

Bacteria from the genus Methylobacterium interact symbiotically (endophytically and epiphytically) with different plant species. These interactions can promote plant growth or induce systemic resistance, increasing plant fitness. The plant colonization is guided by molecular communication between bacteria-bacteria and bacteria-plants, where the bacteria recognize specific exuded compounds by other bacteria (e.g. homoserine molecules) and/or by the plant roots (e.g. flavonoids, ethanol and methanol), respectively. In this context, the aim of this study was to evaluate the effect of quorum sensing molecules (N-acyl-homoserine lactones) and plant exudates (including ethanol) in the expression of a series of bacterial genes involved in Methylobacterium-plant interaction. The selected genes are related to bacterial metabolism (mxaF), adaptation to stressful environment (crtI, phoU and sss), to interactions with plant metabolism compounds (acdS) and pathogenicity (patatin and phoU). Under in vitro conditions, our results showed the differential expression of some important genes related to metabolism, stress and pathogenesis, thereby AHL molecules up-regulate all tested genes, except phoU, while plant exudates induce only mxaF gene expression. In the presence of plant exudates there is a lower bacterial density (due the endophytic and epiphytic colonization), which produce less AHL, leading to down regulation of genes when compared to the control. Therefore, bacterial density, more than plant exudate, influences the expression of genes related to plant-bacteria interaction.

Analysis of 16S rRNA and mxaF genes reveling insights into Methylobacterium niche-specific plant association

The genus Methylobacterium comprises pink-pigmented facultative methylotrophic (PPFM) bacteria, known to be an important plant-associated bacterial group. Species of this group, described as plant-nodulating, have the dual capacity of producing cytokinin and enzymes, such as pectinase and cellulase, involved in systemic resistance induction and nitrogen fixation under specific plant environmental conditions. The aim hereby was to evaluate the phylogenetic distribution of Methylobacterium spp. isolates from different host plants. Thus, a comparative analysis between sequences from structural (16S rRNA) and functional mxaF (which codifies for a subunit of the enzyme methanol dehydrogenase) ubiquitous genes, was undertaken. Notably, some Methylobacterium spp. isolates are generalists through colonizing more than one host plant, whereas others are exclusively found in certain specific plant-species. Congruency between phylogeny and specific host inhabitance was higher in the mxaF gene than in the 16S rRNA, a possible indication of function-based selection in this niche. Therefore, in a first stage, plant colonization by Methylobacterium spp. could represent generalist behavior, possibly related to microbial competition and adaptation to a plant environment. Otherwise, niche-specific colonization is apparently impelled by the host plant.

Specific plant induced biofilm formation in Methylobacterium species

Two endophytic strains of Methylobacterium spp. were used to evaluate biofilm formation on sugarcane roots and on inert wooden sticks. Results show that biofilm formation is variable and that plant surface and possibly root exudates have a role in Methylobacterium spp. host recognition, biofilm formation and successful colonization as endophytes.

Colonization of rice and Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae) larvae by genetically modified endophytic Methylobacterium mesophilicum

The colonization of Spodoptera frugiperda J.E. Smith larvae and rice seedlings by genetically modified endophytic bacterium Methylobacterium mesophilicum, and also the possible transfer of this bacterium to inside the larva's body during seedlings consumption were studied. The data obtained by bacterial reisolation and fluorescence microscopy showed that the bacterium colonized the rice seedlings, the larva's body and that the endophytic bacteria present in seedlings could be acquired by the larvae. In that way, the transference of endophytic bacterium from plants to insect can be a new and important strategy to insect control using engineered microorganisms.

Genetic and metabolic diversity of pink-pigmented facultative methylotrophs in phyllosphere of tropical plants

Diversity of Pink-Pigmented Facultative Methylotrophs (PPFMs) in phyllosphere of cotton, maize and sunflower was determined based on differential carbon-substrate utilization profile and Random Amplified Polymorphic DNA data. Results indicate that six diversified groups of PPFMs are found in these crops. Sunflower and maize phyllosphere harbor four different groups of methylobacteria while cotton has only two groups.

A diversidade de microrganismos metilotróficos facultativos pigmentados (PPFMs) na filosfera de algodão, milho e girassol foi determinada baseada no perfil diferencial de utilização de substratos de carbono e em dados de RAPD. Os resultados indicaram a existência de seis grupos diferentes de PPFMs nessas plantas. As filosferas de girassol e milho apresentaram quatro grupos diferentes de metilobactérias enquanto a de algodão apresentou apenas dois grupos.