Silica deposition and phenotypic changes to Thermus thermophilus cultivated in the presence of supersaturated silicia

Abstract

Thermus thermophilus cells formed siliceous deposits in the presence of supersaturated silicic acid (600 p.p.m SiO 2 ). The supersaturated silicic acid promoted interaction between cells and the inside walls of glass culture bottles, leading to the development of cell aggregates or biofilms. Electron probe microanalysis showed that within the aggregates most of the cell surfaces were covered with silica. Under these conditions, there was remarkable production of silica-induced protein (Sip), a solute-binding component of the Fe 3 þ -binding ABC transporter. Furthermore, supersaturated silica enhanced resistance to the peptide antibiotics bacitracin, colistin and polymyxin B, which all act on the cell envelope. By contrast, supersaturated silica did not induce resistance to ampicillin, chloramphenicol, kanamycin and tetracycline, which inhibit peptide synthesis. Although strong expression of Sip was detected in liquid cultures of T. thermophilus in the presence of supersaturated silica and colistin, upregulated transcription of putative efflux pump and multidrug resistance ABC transporter genes were not detected by quantitative real-time PCR analysis. These findings suggest Sip promotes silica deposition on the surfaces of cells, after which the silicified outer membrane may serve as a 'suit-of-armor,' conferring resistance to peptide antibiotics.

Experimental fossilization of the Thermophilic Gram-positive BacteriumGeobacillusSP7A: A Long Duration Preservation Study

“…In a silicifying environment, cells can change their metabolisms (through protein expression, modification of the cell wall properties, production of EPS), thus implementing a survival strategy that limits the detrimental effects of the fossilization (i.e., blocking of exchange with the surrounding environment, damage to cell structure and eventually death) Lalonde et al 2005;Saw et al 2008;Iwai et al 2010). In particular, while encapsulating a close relative to Geobacillus SP7A (the thermophilic Anoxybacillus flavithermus), Saw et al (2008) noticed the ability of this species to survive silicification and to adapt its metabolism accordingly.…”

“…Recently, microbial response to silicification has been investigated and it has been shown that microorganisms can implement various strategies to deal with a silica saturated environment (Iwai et al 2010;Konhauser et al 2008;Lalonde et al 2005;Saw et al 2008). The main effect of these strategies is that mineralization is limited to the outer part of the cell wall (Phoenix et al 2000), thus allowing the cell to continue to live.…”

The Thermus thermophilus comEA/comEC operon is associated with DNA binding and regulation of the DNA translocator and type IV pili

“…cDNA was generated and used for quantitative real-time PCR {SYBR Green qPCR Kits [(2×) without ROX]} (Fisher Scientific GmbH, Schwerte, Germany). The amplification conditions were 300 s at 98°C followed by 40 cycles at 98°C for 30 s, annealing at 67°C for 15 s and an elongation at 72°C for 15 s. To exclude changes in expression, two recently published house-keeping genes, encoding glutamate-dehydrogenase B (TTC1211) and gyrase subunit B (TTC1622), were used (Cava et al, 2008;Iwai et al, 2010). To determine the changes in mRNA expression levels, the comparative threshold cycle (Ct) method (2 −ΔΔCt ) was used (Livak and Schmittgen, 2001;Schmittgen and Livak, 2008).…”

Silica-Induced Protein (Sip) in Thermophilic Bacterium Thermus thermophilus Responds to Low Iron Availability

“…Primer design and the PCR conditions were the same as described previously (19). The primers used are listed in Table S1 in the supplemental material.…”

“…After cultivation for an additional 1 h at 70°C, the cultures were collected, treated with RNAprotect Bacteria reagent (Qiagen, Hilden, Germany), and stored at Ϫ80°C until needed. Total RNA extraction and purification were carried out as described previously (19).…”