Vanadium pollution thus raises serious marine environmental concerns. High levels of V have been found in coastal sediment (Beg et al., 2001). Vanadium (especially as VOSO4) is toxic to the mammalian respiratory system (Wörle-Knirsch et al., 2007) and also exerts adverse physiological effects on various microbes (Fukuda & Yamase, 1997; Aendekerk et al., 2002; Denayer et al., 2006). Bacterial
resistance to V can be caused by mutations in efflux pump (Aendekerk et al., 2002) and tricarboxylic acid (TCA) cycle enzymes (Denayer et al., 2006). In contrast, some V-containing metabolic enzymes have been identified in both PD98059 cell line eukaryotes (Rehder, 1992) and soil and enteric bacteria (van Marwijk et al., 2009; Lee et al., 2010), and it appears that V serves as an essential trace element in these organisms. However, the effect of V pollution on the marine microbial ecosystem is unknown. In some cases, antibiotic resistance can be correlated with metal exposure (Baker-Austin et al., 2006; Stepanauskas et al., 2006). Exposure to toxic metals such as cadmium (Cd) and nickel (Ni) represents a selective pressure that may lead to the development of antibiotic resistance (Stepanauskas et al.,
2006), and major resistance mechanisms ALK inhibitor are based on common efflux of metals and antibiotics and a reduction in permeability (Baker-Austin et al., 2006). Some metals, such as Ca2+ and Mg2+, are capable of inducing competence at millimolar concentrations (Takeo, 1972; Page & von Tigerstrom, 1979), resulting in accelerated DNA intake by bacteria and horizontal gene transfer (HGT) between bacteria. We therefore hypothesized that V contamination in the ocean may facilitate development
of antibiotic resistance through HGT. To determine the how exposure to V and other metals influences the acquisition of antibiotic resistance, we cultured oxytetracycline (OTC)-sensitive Escherichia coli in the presence of OTC-resistant Photobacterium. Then the occurrence rate of OTC resistant-E. coli was enumerated. Transfer of the tetracycline resistance gene, tet(M), was also confirmed in transconjugants. Furthermore, the concentration of V and the rate of OTC resistance in natural marine sediment were quantified. The marine bacterium Photobacterium damselae subspecies damselae strain 04Ya311, first reported as a Vibrio sp. (Neela et al., 2007), was used as the donor of Methane monooxygenase the tet(M) gene. It has already been confirmed that transfer of tet(M) from P. damselae 04Ya311 to E. coli occurs through mating (Neela et al., 2009) via the conjugative plasmid pAQU1 (Nonaka et al., 2012), and this transfer is reversible. Mating gene-transfer experiments were performed as described previously (Neela et al., 2009) with E. coli JM109, which does not possess tet(M), serving as the recipient strain. The ratio of donor to recipient cells in the mating experiment was 10−3 : 1 because of the high conjugation rate (6.49 ± 1.97 × 10−3, n = 3) in the absence of V.