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April 21, 2020  |  

Genome Organization and Adaptive Potential of Archetypal Organophosphate Degrading Sphingobium fuliginis ATCC 27551.

Sphingobium fuliginis ATCC 27551, previously classified as Flavobacterium sp. ATCC 27551, degrades neurotoxic organophosphate insecticides and nerve agents through the activity of a membrane-associated organophosphate hydrolase. This study was designed to determine the complete genome sequence of S. fuliginis ATCC 27551 to unravel its degradative potential and adaptability to harsh environments. The 5,414,624?bp genome with a GC content of 64.4% is distributed between two chromosomes and four plasmids and encodes 5,557 proteins. Of the four plasmids, designated as pSF1, pSF2, pSF3, and pSF4, only two (pSF1 and pSF2) are self-transmissible and contained the complete genetic repertoire for a T4SS. The other two plasmids (pSF3 and pSF4) are mobilizable and both showed the presence of an oriT and relaxase-encoding sequences. The sequence of plasmid pSF3 coincided with the previously determined sequence of pPDL2 and included an opd gene encoding organophosphate hydrolase as a part of the mobile element. About 15,455 orthologous clusters were identified from among the cumulatively annotated genes of 49 Sphingobium species. Phylogenetic analysis done using the core genome consisting of 802 orthologous clusters revealed a close relationship between S. fuliginis ATCC 27551 and bacteria capable of degradation of polyaromatic hydrocarbon compounds. Genes coding for transposases, efflux pumps conferring resistance to heavy metals, and TonR-type outer membrane receptors are selectively enriched in the genome of S. fuliginis ATCC 27551 and appear to contribute to the adaptive potential of the organism to challenging and harsh environments. © The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

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April 21, 2020  |  

Genome Comparisons of Wild Isolates of Caulobacter crescentus Reveal Rates of Inversion and Horizontal Gene Transfer.

Since previous interspecies comparisons of Caulobacter genomes have revealed extensive genome rearrangements, we decided to compare the nucleotide sequences of four C. crescentus genomes, NA1000, CB1, CB2, and CB13. To accomplish this goal, we used PacBio sequencing technology to determine the nucleotide sequence of the CB1, CB2, and CB13 genomes, and obtained each genome sequence as a single contig. To correct for possible sequencing errors, each genome was sequenced twice. The only differences we observed between the two sets of independently determined sequences were random omissions of a single base in a small percentage of the homopolymer regions where a single base is repeated multiple times. Comparisons of these four genomes indicated that horizontal gene transfer events that included small numbers of genes occurred at frequencies in the range of 10-3 to 10-4 insertions per generation. Large insertions were about 100 times less frequent. Also, in contrast to previous interspecies comparisons, we found no genome rearrangements when the closely related NA1000, CB1, and CB2 genomes were compared, and only eight inversions and one translocation when the more distantly related CB13 genome was compared to the other genomes. Thus, we estimate that inversions occur at a rate of one per 10 to 12 million generations in Caulobacter genomes. The inversions seem to be complex events that include the simultaneous creation of indels.

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April 21, 2020  |  

Genomic Characterization of a Newly Isolated Rhizobacteria Sphingomonas panacis Reveals Plant Growth Promoting Effect to Rice

This article reports the full genome sequence of Sphingomonas panacis DCY99T (=KCTC 42347T =JCM30806T), which is a Gram-negative rod-shaped, non-spore forming, motile bacterium isolated from rusty ginseng root in South Korea. A draft genome of S. panacis DCY99T and a single circular plasmid were generated using the PacBio platform. Antagonistic activity experiment showed S. panacis DCY99T has the plant growth promoting effect. Thus, the genome sequence of S. panacis DCY99T may contribute to biotechnological application of the genus Sphingomonas in agriculture.

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April 21, 2020  |  

Denitrifying Bacteria Active in Woodchip Bioreactors at Low-Temperature Conditions.

Woodchip bioreactor technology removes nitrate from agricultural subsurface drainage by using denitrifying microorganisms. Although woodchip bioreactors have demonstrated success in many field locations, low water temperature can significantly limit bioreactor efficiency and performance. To improve bioreactor performance, it is important to identify the microbes responsible for nitrate removal at low temperature conditions. Therefore, in this study, we identified and characterized denitrifiers active at low-temperature conditions by using culture-independent and -dependent approaches. By comparative 16S rRNA (gene) analysis and culture isolation technique, Pseudomonas spp., Polaromonas spp., and Cellulomonas spp. were identified as being important bacteria responsible for denitrification in woodchip bioreactor microcosms at relatively low temperature conditions (15°C). Genome analysis of Cellulomonas sp. strain WB94 confirmed the presence of nitrite reductase gene nirK. Transcription levels of this nirK were significantly higher in the denitrifying microcosms than in the non-denitrifying microcosms. Strain WB94 was also capable of degrading cellulose and other complex polysaccharides. Taken together, our results suggest that Cellulomonas sp. denitrifiers could degrade woodchips to provide carbon source and electron donors to themselves and other denitrifiers in woodchip bioreactors at low-temperature conditions. By inoculating these denitrifiers (i.e., bioaugmentation), it might be possible to increase the nitrate removal rate of woodchip bioreactors at low-temperature conditions.

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