high-resolution-comparison-of-bacterial-conjugation-frequencies

High-Resolution Comparison of Bacterial Conjugation Frequencies

Bacterial conjugation is an important step in the horizontal transfer of antibiotic resistance genes via a conjugative DNA element. In-depth comparisons ...

Shizuoka University

Bioaugmentation is an effective treatment to clean up polluted sites using contaminant-degrading bacteria. However, this treatment is influenced by various environmental conditions, including temperature. In this study, an effective bioaugmentation system under low temperature condition was developed with three Rhodococcus (strains A, C, and D) and one Gordonia (strain B) oil-degraders, which are officially permitted for bioaugmentation applications in Japan. The oil-degrading ability of each strain and mixture was assessed in liquid culture and in model soils supplemented with A-fuel oil. In liquid culture, Rhodococcus strains A and C degraded the A-fuel oil in cold temperature conditions (15°C and 10°C) as well as in mesophilic condition (30°C). In the model soil samples, the mixture of four degraders was the most effective at removing the A-fuel oil under mesophilic condition (>90%), suggesting that strains B and/or D might have factors that promote degradation. In contrast, A-fuel oil was efficiently removed (>80%) in the soil samples inoculated with A or C as well as that with mixture in cold temperature condition, suggesting that strains A and C were the major degraders under cold condition. Our results indicate that the four degraders could be applied to the bioaugmentation in cold areas.

Biodegradation of A-fuel oil in soil samples with bacterial mixtures of Rhodococcus and Gordonia strains under low temperature conditions.

Novel self-transmissible plasmids were exogenously captured from environmental samples by triparental matings with pBBR1MCS-2 as a mobilizable plasmid and  as a recipient. A total of 272 recipients were successfully obtained as plasmid host candidates from granules of an anaerobic methane fermentation plant and from cow manure. The whole nucleotide sequences of six plasmids were determined, including one IncP-1 plasmid (pSN1104-59), four PromA-like plasmids (pSN1104-11, pSN1104-34, pSN0729-62, and pSN0729-70), and one novel plasmid (pSN1216-29), whose incompatibility group has not been previously identified. No previously known antibiotic resistance genes were found in these plasmids. In-depth phylogenetic analyses showed that the PromA-like plasmids belong to subgroups of PromA (designated as PromAγ and PromAδ) different from previously proposed subgroups PromAα and PromAβ. Twenty-four genes were identified as backbone genes by comparisons with other PromA plasmids. The nucleotide sequences of pSN1216-29 share high identity with those found in clinical isolates. A minireplicon of pSN1216-29 was successfully constructed from  encoding a replication initiation protein and . All the captured plasmids were found to have a broad host range and could be transferred to and replicated in different classes of . Notably,  and  of pSN1216-29 showed high similarity with one of two replication systems of pSRC119-A/C, known as a plasmid with multidrug resistance genes found in  serovar Senftenberg. Our findings suggest that these "cryptic" but broad-host-range plasmids may be important for spreading several genes as "vehicles" in a wider range of bacteria in natural environments.

Novel Self-Transmissible and Broad-Host-Range Plasmids Exogenously Captured From Anaerobic Granules or Cow Manure.

Large-scale processing of lignocellulosics for glucose production generally relies on high temperature and acidic or alkaline conditions. However, extreme conditions produce chemical contaminants that complicate downstream processing. A method that mainly rely on mechanical and enzymatic reaction completely averts such problem and generates unmodified lignin. Products from this process could find novel applications in the chemicals, feed and food industry. But a large-scale system suitable for this purpose is yet to be developed. In this study we applied simultaneous enzymatic saccharification and communition (SESC) for the pre-treatment of a representative lignocellulosic biomass, cedar softwood, under both laboratory and large-scale conditions.

Kazuhide Kimbara

Applied Chemistry and Biochemical Engineering Course,
Department of Engineering,
Graduate School of Integrated Science and Technology,
Applied Chemistry and Biochemical Engineering Course, Department of Engineering, Graduate School of Integrated Science and Technology

Shizuoka University

High-Resolution Comparison of Bacterial Conjugation Frequencies