Plasmid transfer between strains of Pseudomonas putida, and their survival, within a pilot scale percolating-filter sewage treatment system

Abstract

The ability of non-indigenous bacteria to survive and conjugate within a fully functioning pilot-scale percolating filter bed, with a substantial biofilm and a diverse invertebrate community, was investigated.Pseudomonas putida UWC8, harbouring the conjugative plasmid pQKH6, isolated from river epilithon, and P. putidu UWC9 were introduced and survived in a culturable state for up to 145 days. During this time plasmid transfer, with transfer frequencies of up to 6.54 X lo-' cfu per recipient, could be detected. The macro-invertebrate community was also investigated. The invertebrate grazers had no detectable effect upon the densities of the introduced bacteria.

Using microcosms to study gene transfer in aquatic habitats

“… Appearance of transconjugants in biofilms after inoculation of donor and/or recipients into stream microcosms [20, 41][J.R. Marchesi, M.J. Day and J.C. Fry, unpublished], and a comparison with equivalent data obtained from a percolating filter‐bed microcosm simulating an analogous environment [44]; nd = no transconjugants detected; pQM901 = pQKH6::Tn 5 :: tdn C; pQM902 = pQKH6::Tn 5 :: mer :: tdn C. …”

“…A modified version of the microcosm used by Houston et al [43] was employed by Ashelford et al [44] to investigate gene transfer in percolating‐filter sewage‐beds. The microcosm was of a similar depth to a full‐scale bed, but much narrower (Fig.…”

“…It quickly became integrated into the filter biofilm, but slowly died or was washed out, declining to about 0.1% of the initial density after 60 days (Fig. 6; [44]). The plasmid was very stable over this period and was not lost from its host; this segregational stability is typical of almost all the plasmids from epilithon we have investigated.…”

Non-invasive determination of conjugative transfer of plasmids bearing antibiotic-resistance genes in biofilm-bound bacteria: effects of substrate loading and antibiotic selection

“…Horizontal gene transfer (HGT) is considered to be the most dominant mechanism for bacteria to rapidly adapt to changing environments by spreading genetic information (Ashelford 1998; Dahlberg et al 1998; Ravatn et al 1998). Effects of environmental selection pressure on conjugational plasmid transfer have gained considerable interest recently because it is now generally realized that “selection-free” situations are hard to achieve (Top et al 1995; Hohnstock et al 2000; Pinedo and Smets 2005; Slater et al 2008).…”

Mycelia as a focal point for horizontal gene transfer among soil bacteria

“…Conjugation, i.e. the direct transfer of mobile genetic elements such as plasmids from a donor to a recipient cell, is considered to be the most important HGT mechanism56. Conjugation in soil is influenced by various factors such as donor-recipient compatibility, nutrient availability, temperature and pH; spatial isolation of cell aggregates and biofilm patches, and the restricted mobility of bacteria in the porous soil environment impede bacterial conjugation789101112.…”