Mechanisms of Horizontal Gene Transfer

Horizontal gene transfer plays important roles in the evolution of S. aureus, and indeed, a variety of virulence factors and antibiotic resistance genes are embedded in a series of mobile genetic elements. In this chapter, we review the mechanisms of horizontal gene transfer, including recent findings on the natural genetic competence. Then, we consider the transfer of two important antibiotic resistance genes: the methicillin resistance gene, mecA (in Staphylococcal Cassette Chromosome) and the linezolid resistance gene, cfr (in plasmid). In either case, distinct mechanisms driving the gene dissemination support the prominent evolutionary ability of this important human pathogen

Argulus coregoni（Branchiura: Argulidae）parasitic on ayu, Plecoglossus altivelis altivelis, in the Takatsu River, Shimane Prefecture, Japan

An adult female of the argulid branchu-rian Argulus coregoni Thorell, 1864 was collected from the body surface of ayu, Plecoglossus altivelis altivelis, in the Takatsu River, Shimane Prefecture, JapaninSeptember 2011. This is the first record of A. coregoni from ayu in Shimane Prefecture.ホシザキグリーン財団委託業績 第131

Fitness of Spontaneous Rifampicin-Resistant Staphylococcus aureus Isolates in a Biofilm Environment

Biofilms of S. aureus accumulate cells resistant to the antibiotic rifampicin. We show here that the accumulation of rifampicin resistant mutants (RifR) in biofilms is not equable but rather is a local event, suggesting that the growth of a few locally emerged mutants is responsible for this. Competition assays demonstrated that, compared to wild-type bacteria, the isolated RifR mutants have a growth advantage in biofilms, but not in planktonic culture. To gain insight into the mechanism of the growth advantage, we tested the involvement of the two-component systems (TCS) that sense and respond to environmental changes. We found that a deletion of SrrAB or NreBC has a drastic effect on the growth advantage of RifR mutants, suggesting the importance of oxygen/respiration responses. All six of the RifR isolates tested showed increased resistance to at least one of the common stresses found in the biofilm environment (i.e., oxidative, nitric acid, and organic acid stress). The RifR mutants also had a growth advantage in a biofilm flow model, which highlights the physiological relevance of our findings

Argulus coregoni (Branchiura: Argulidae) parasitic on ayu, Plecoglossus altivelis altivelis (Plecoglossidae), in central Honshu, Japan

Argulus coregoni Thorell, 1864 was collected from the body surface of ayu, Plecoglossus altivelis altivelis (Temminck & Schlegel, 1846), from six rivers in Gifu, Achi, Mie, and Shiga prefectures, central Honshu, Japan. The collection of A. coregoni from Mie Prefecture represents its new prefectural record. Salmonids have been regarded as the major hosts of A. coregoni in Japanese rivers, but the present collections suggest that ayu is also important as a riverine host of the parasite

Circadian-regulated expression of a nuclear-encoded plastid σ factor gene (sigA) in wheat seedlings

AbstractThe activity of a light-responsive psbD promoter in plastids is known to be regulated by a circadian clock. However, the mechanism of the circadian regulation of the psbD light-responsive promotor, which is recognized by an Escherichia coli-type RNA polymerase, is not yet known. We examined the time course of mRNA accumulation of two E. coli-type RNA polymerase subunit genes, sigA and rpoA, under a continuous light condition after 12 h light/12 h dark entrainment. Accumulation of the sigA mRNA was found to be regulated by a circadian clock, while rpoA mRNA did not show any significant oscillation throughout the experiment

Identification of nucleoid associated proteins (NAPs) under oxidative stress in Staphylococcus aureus

BackgroundBacterial nucleoid consists of genome DNA, RNA, and hundreds of nucleoid-associated proteins (NAPs). Escherichia coli nucleoid is compacted towards the stationary phase, replacing most log-phase NAPs with the major stationary-phase nucleoid protein, Dps. In contrast, Staphylococcus aureus nucleoid sustains the fiber structures throughout the growth. Instead, the Dps homologue, MrgA, expresses under oxidative stress conditions to clump the nucleoid, but the composition of the clumped nucleoid was elusive.ResultsThe staphylococcal nucleoid under oxidative stress was isolated by sucrose gradient centrifugation, and the proteins were analyzed by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). We identified 299 proteins in the nucleoid under oxidative stress, including 113 csNAPs (contaminant-subtracted NAPs). Comparison with the previously identified csNAPs in log- and stationary phase indicated that one fifth of the csNAPs under oxidative stress were the constitutive nucleoid components; importantly, several factors including HU, SarA, FabZ, and ribosomes were sustained under oxidative stress. Some factors (e.g. SA1663 and SA0092/SA0093) with unknown functions were included in the csNAPs list specifically under oxidative stress condition.ConclusionNucleoid constitutively holds Hu, SarA, FabG, and ribosomal proteins even under the oxidative stress, reflecting the active functions of the clumped nucleoid, unlikely to the dormant E. coli nucleoid compacted in the stationary phase or starvation

Permanent pacemaker lead placement via the femoral vein in an elderly patient with a large thoracic aortic aneurysm

AbstractAn 87-year-old woman with complete atrioventricular block was admitted for permanent pacemaker implantation. The patient had a large thoracic aortic aneurysm that had been conservatively treated. Lead placement was not possible via the superior vena cava or the epicardial route because of the aneurysm. Therefore, we implanted a VVI pacemaker via the femoral approach. A unit was placed in a pouch on the right lower abdominal wall, and a lead was introduced into the right ventricle via the right femoral vein. The femoral vein approach is rarely used; however, it should be recognized as an effective alternative when the usual approach is difficult or impossible to be performed

Adjacent-possible ecological niche: growth of Lactobacillus species co-cultured with Escherichia coli in a synthetic minimal medium

In certain conditions, members of the Lactobacillus genus are auxotrophs that have fastidious requirements for growth. Notably, Lactobacillus cannot grow in M9 medium, a minimal synthetic medium used for Escherichia coli. However, we found that some Lactobacillus strains can be grown in M9 when co-cultured with E. coli K-12. In the co-culture, L. casei proliferates exponentially, reaching cell densities of 108 CFU (colony-forming unit) ml−1 in 6 h and dominating E. coli in the late growth phase. Spent medium from E. coli grown overnight lacked this growth-promoting effect on L. casei. Similarly, the effect was not observed when the species were separated by a 0.4-µm membrane. Microscopic observations showed that L. casei are embedded in the micro-scale clusters of E. coli in the early growth phase. This study describes for the first time the ability of a Lactobacillus species to grow in minimal medium when in close proximity with co-cultured bacteria