Transcriptional Analysis of Biofilm Formation Processes in the Anaerobic, Hyperthermophilic BacteriumThermotoga maritima

Abstract

Thermotoga maritima, a fermentative, anaerobic, hyperthermophilic bacterium, was found to attach to bioreactor glass walls, nylon mesh, and polycarbonate filters during chemostat cultivation on maltose-based media at 80°C. A whole-genome cDNA microarray was used to examine differential expression patterns between biofilm and planktonic populations. Mixed-model statistical analysis revealed differential expression (twofold or more) of 114 open reading frames in sessile cells (6% of the genome), over a third of which were initially annotated as hypothetical proteins in the T. maritima genome. Among the previously annotated genes in the T. maritima genome, which showed expression changes during biofilm growth, were several that corresponded to biofilm formation genes identified in mesophilic bacteria (i.e., Pseudomonas species, Escherichia coli, and Staphylococcus epidermidis). Most notably, T. maritima biofilm-bound cells exhibited increased transcription of genes involved in iron and sulfur transport, as well as in biosynthesis of cysteine, thiamine, NAD, and isoprenoid side chains of quinones. These findings were all consistent with the up-regulation of iron-sulfur cluster assembly and repair functions in biofilm cells. Significant up-regulation of several ␤-specific glycosidases was also noted in biofilm cells, despite the fact that maltose was the primary carbon source fed to the chemostat. The reasons for increased ␤-glycosidase levels are unclear but are likely related to the processing of biofilm-based polysaccharides. In addition to revealing insights into the phenotype of sessile T. maritima communities, the methodology developed here can be extended to study other anaerobic biofilm formation processes as well as to examine aspects of microbial ecology in hydrothermal environments.

The Thermotoga maritima Phenotype Is Impacted by Syntrophic Interaction with Methanococcus jannaschii in Hyperthermophilic Coculture

“…In previous studies with T. maritima, it was noted that A was up-regulated in biofilm cells compared to planktonic cells (35) and under conditions of heat stress (34). In this study,…”

“…In syntrophic coculture with a hydrogenotrophic methanogen, such as Methanococcus jannaschii (7), this inhibition is relieved and cell population density is enhanced through the interspecies transfer of hydrogen (26). In addition to the utilization of sugars as carbon and energy sources (8, 28), T. maritima also has been shown to produce exopolysaccharides (EPS) that serve as the basis for biofilms (35,36). In fact, when grown to high cell densities through coculture with the hyperthermophilic methanogen M. jannaschii, T. maritima produces EPS that leads to formation of stable cellular aggregates, which presumably facilitate interspecies H 2 transfer (26).…”

Transcriptional and translational expression patterns associated with immobilized growth of Campylobacter jejuni

“…To our knowledge there have been no previous connections proposed between either low-iron adaptation or biofilm formation and amino acid transport and metabolism, although amino acid starvation was identified as a trigger for biofilm formation for Candida albicans (Garcia-Sanchez et al, 2004). The induction of ABC transport systems which are not specific to amino acid transport has been reported as a consequence of biofilm formation (Pysz et al, 2004) although the functional relevance remains unclear.…”

“…Induction of iron-uptake systems has not emerged as a conserved response within investigations of biofilms, although it has been reported for select biofilms (Pysz et al, 2004). The availability of iron does however represent a central consideration in the decision to commit to biofilm formation; iron chelation through lactoferrin has been shown to discourage Pseudomonas aeruginosa biofilm formation.…”

Transcription Factor Nrg1 Mediates Capsule Formation, Stress Response, and Pathogenesis inCryptococcus neoformans

“…Extracted microarray data from the second array were imported into a statistical software package (SAS v8; SAS Institute, Cary, NC), and initial background subtraction was performed. Mixed model analysis of microarray data (54) was used to evaluate differential expression data using approaches presented elsewhere (10,40,42). We calculated the statistical significance of each genetic element using least squares estimates of gene-specific treatment effects across pairs of treatments obtained for each gene under each treatment condition.…”