Occurrence of antibiotic and metal resistance and plasmids in Bacillus strains isolated from marine sediment

Abstract

Eleven hundred Bacillus strains isolated from marine sediment from the Minas Basin, Nova Scotia, Canada, were purified on LB agar supplemented with ampicillin, chloramphenicol, erythromycin, streptomycin, tetracycline, or mercuric chloride. Seventy-seven isolates were examined for plasmid DNA, and for resistance to 11 antibiotics, HgCl2, and phenylmercuric acetate. Minimum inhibitory concentrations of Ag, Cd, Co, Cu, and Zn were also determined. Forty-three percent of antibiotic- and mercury-resistant strains contained one or more plasmids ranging from 1.9 to 210 MDa. Fifty-four percent carried plasmids greater than 20 MDa, and 97% were resistant to two or more metals. There was no correlation between plasmid content and resistance either to antibiotics or to mercurial compounds in these strains. Mercury-resistant isolates were unable to transform Hg2+ to volatile Hg0 by virtue of a mercuric reductase enzyme system (mer). Strains resistant to Hg2+ were investigated for their ability to produce H2S and intracellular acid-labile sulfide when grown in the absence and presence of HgCl2. Lower levels of H2S and intracellular sulfide were detected only in metal-resistant strains grown in the presence of HgCl2, suggesting that cellular sulfides complexed with Hg2+ in these strains.

Differentiation of plasmids in marine diazotroph assemblages determined by randomly amplified polymorphic DNA analysis

“…The presence of plasmids in marine sediment and watercolumn bacterial populations is well documented (Kobori et al, 1984 ;Hermansson et al, 1987 ;Belliveau et al, 1991 ;Aviles et al, 1993 ;Dahlberg et al, 1997). In contrast to efforts to characterize plasmid populations from the rhizoplane of terrestrial plants (Lilley et al, 1996 ;van Elsas et al, 1998), few studies have characterized plasmid distribution and diversity in bacterial assemblages associated with the roots and rhizomes of salt marsh macrophytes.…”

Microbial Resistance to Metals in the Environment

“…These reports included mostly aerobic microorganisms, with prominent examples being resistance in Staphylococcaus sp., Escherichia coli, Pseudomonas aeruginosa, and Bacillus sp. (Nakahara et al, 1977;Marques et al, 1979;Harnett and Gyles, 1984;Schwarz and Hobel, 1989;Belliveau et al, 1991;Wang and Shen, 1995). Resistance has been reported for mercury [Hg(II)] and organomercurials in obligate anaerobes like Bacteroides and Clostridium species.…”

“…They arose because bacteria exist in an environment that has always contained metals. Metal resistance is often associated with antibiotic resistance (Nakahara et al, 1977;Harnett and Gyles, 1984;McEntee et al, 1986;Schwarz and HoK bel, 1989;Belliveau et al, 1991). Resistance to both can be transferred among organisms through conjugation or transduction (Harnett and Gyles, 1984).…”

Mercury Tolerance of Thermophilic Bacillus sp. and Ureibacillus sp

“…are exhibiting mercury tolerance mechanisms. Several organisms have been reported as being mercury tolerant due to HgS precipitation (PanHou & Imura 1981, Aiking et al 1985, Belliveau et al 1991, Baldi et al 1993. HgS can be formed by various mechanisms.…”