@article{nichols_johnson_chou_kelly_2009, title={Temperature, not LuxS, mediates AI-2 formation in hydrothermal habitats}, volume={68}, ISSN={["1574-6941"]}, DOI={10.1111/j.1574-6941.2009.00662.x}, abstractNote={Quorum sensing provides the basis for coordinating community-wide, microbial behaviors in many mesophilic bacteria. However, little attention has been directed toward the possibility that such phenomena occur in extremely thermal microbial environments. Despite the absence of luxS in hyperthermophile genomes, autoinducer-2 (AI-2), a boronated furanone and proposed 'universal' interspecies mesophilic bacterial communication signal, could be formed by Thermotoga maritima and Pyrococcus furiosus through a combination of biotic and abiotic reaction steps. AI-2 did not, however, induce any detectable quorum-sensing phenotypes in these organisms, although transcriptome-based evidence of an AI-2-induced stress response was observed in T. maritima. The significance, if any, of AI-2 in hydrothermal habitats is not yet clear. Nevertheless, these results show the importance of considering environmental factors, in this case high temperatures, as abiotic causative agents of biochemical and microbiological phenomena.}, number={2}, journal={FEMS MICROBIOLOGY ECOLOGY}, author={Nichols, Jason D. and Johnson, Matthew R. and Chou, Chung-Jung and Kelly, Robert M.}, year={2009}, month={Apr}, pages={173–181} }
 @article{madding_michel_shockley_conners_epting_johnson_kelly_2007, title={Role of the beta 1 subunit in the function and stability of the 20S proteasome in the hyperthermophilic archaeon Pyrococcus furiosus}, volume={189}, ISSN={["0021-9193"]}, DOI={10.1128/JB.01382-06}, abstractNote={ABSTRACT The hyperthermophilic archaeon Pyrococcus furiosus genome encodes three proteasome component proteins: one α protein (PF1571) and two β proteins (β1-PF1404 and β2-PF0159), as well as an ATPase (PF0115), referred to as proteasome-activating nucleotidase. Transcriptional analysis of the P. furiosus dynamic heat shock response (shift from 90 to 105°C) showed that the β1 gene was up-regulated over twofold within 5 minutes, suggesting a specific role during thermal stress. Consistent with transcriptional data, two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that incorporation of the β1 protein relative to β2 into the 20S proteasome (core particle [CP]) increased with increasing temperature for both native and recombinant versions. For the recombinant enzyme, the β2/β1 ratio varied linearly with temperature from 3.8, when assembled at 80°C, to 0.9 at 105°C. The recombinant α+β1+β2 CP assembled at 105°C was more thermostable than either the α+β1+β2 version assembled at 90°C or the α+β2 version assembled at either 90°C or 105°C, based on melting temperature and the biocatalytic inactivation rate at 115°C. The recombinant CP assembled at 105°C was also found to have different catalytic rates and specificity for peptide hydrolysis, compared to the 90°C assembly (measured at 95°C). Combination of the α and β1 proteins neither yielded a large proteasome complex nor demonstrated any significant activity. These results indicate that the β1 subunit in the P. furiosus 20S proteasome plays a thermostabilizing role and influences biocatalytic properties, suggesting that β subunit composition is a factor in archaeal proteasome function during thermal stress, when polypeptide turnover is essential to cell survival.}, number={2}, journal={JOURNAL OF BACTERIOLOGY}, author={Madding, Lara S. and Michel, Joshua K. and Shockley, Keith R. and Conners, Shannon B. and Epting, Kevin L. and Johnson, Matthew R. and Kelly, Robert M.}, year={2007}, month={Jan}, pages={583–590} }
 @article{montero_lewis_johnson_conners_nance_nichols_kelly_2006, title={Colocation of genes encoding a tRNA-mRNA hybrid and a putative signaling peptide on complementary strands in the genome of the hyperthermophilic bacterium Thermotoga maritima}, volume={188}, ISSN={["0021-9193"]}, DOI={10.1128/JB.00470-06}, abstractNote={ABSTRACT In the genome of the hyperthermophilic bacterium Thermotoga maritima, TM0504 encodes a putative signaling peptide implicated in population density-dependent exopolysaccharide formation. Although not noted in the original genome annotation, TM0504 was found to colocate, on the opposite strand, with the gene encoding ssrA, a hybrid of tRNA and mRNA (tmRNA), which is involved in a trans-translation process related to ribosome rescue and is ubiquitous in bacteria. Specific DNA probes were designed and used in real-time PCR assays to follow the separate transcriptional responses of the colocated open reading frames (ORFs) during transition from exponential to stationary phase, chloramphenicol challenge, and syntrophic coculture with Methanococcus jannaschii. TM0504 transcription did not vary under normal growth conditions. Transcription of the tmRNA gene, however, was significantly up-regulated during chloramphenicol challenge and in T. maritima bound in exopolysaccharide aggregates during methanogenic coculture. The significance of the colocation of ORFs encoding a putative signaling peptide and tmRNA in T. maritima is intriguing, since this overlapping arrangement (tmRNA associated with putative small ORFs) was found to be conserved in at least 181 bacterial genomes sequenced to date. Whether peptides related to TM0504 in other bacteria play a role in quorum sensing is not yet known, but their ubiquitous colocalization with respect to tmRNA merits further examination.}, number={19}, journal={JOURNAL OF BACTERIOLOGY}, author={Montero, Clemente I. and Lewis, Derrick L. and Johnson, Matthew R. and Conners, Shannon B. and Nance, Elizabeth A. and Nichols, Jason D. and Kelly, Robert M.}, year={2006}, month={Oct}, pages={6802–6807} }
 @misc{conners_mongodin_johnson_montero_nelson_kelly_2006, title={Microbial biochemistry, physiology, and biotechnology of hyperthermophilic Thermotoga species}, volume={30}, ISSN={["1574-6976"]}, DOI={10.1111/j.1574-6976.2006.00039.x}, abstractNote={High-throughput sequencing of microbial genomes has allowed the application of functional genomics methods to species lacking well-developed genetic systems. For the model hyperthermophile Thermotoga maritima, microarrays have been used in comparative genomic hybridization studies to investigate diversity among Thermotoga species. Transcriptional data have assisted in prediction of pathways for carbohydrate utilization, iron-sulfur cluster synthesis and repair, expolysaccharide formation, and quorum sensing. Structural genomics efforts aimed at the T. maritima proteome have yielded hundreds of high-resolution datasets and predicted functions for uncharacterized proteins. The information gained from genomics studies will be particularly useful for developing new biotechnology applications for T. maritima enzymes.}, number={6}, journal={FEMS MICROBIOLOGY REVIEWS}, author={Conners, Shannon B. and Mongodin, Emmanuel F. and Johnson, Matthew R. and Montero, Clemente I. and Nelson, Karen E. and Kelly, Robert M.}, year={2006}, month={Nov}, pages={872–905} }
 @article{lee_shockley_schut_conners_montero_johnson_chou_bridger_wigner_brehm_et al._2006, title={Transcriptional and biochemical analysis of starch metabolism in the hyperthermophilic archaeon Pyrococcus furiosus}, volume={188}, ISSN={["1098-5530"]}, DOI={10.1128/JB.188.6.2115-2125.2006}, abstractNote={ABSTRACT Pyrococcus furiosus utilizes starch and its degradation products, such as maltose, as primary carbon sources, but the pathways by which these α-glucans are processed have yet to be defined. For example, its genome contains genes proposed to encode five amylolytic enzymes (including a cyclodextrin glucanotransferase [CGTase] and amylopullulanase), as well as two transporters for maltose and maltodextrins (Mal-I and Mal-II), and a range of intracellular enzymes have been purified that reportedly metabolize maltodextrins and maltose. However, precisely which of these enzymes are involved in starch processing is not clear. In this study, starch metabolism in P. furiosus was examined by biochemical analyses in conjunction with global transcriptional response data for cells grown on a variety of glucans. In addition, DNA sequencing led to the correction of two key errors in the genome sequence, and these change the predicted properties of amylopullulanase (now designated PF1935*) and CGTase (PF0478*). Based on all of these data, a pathway is proposed that is specific for starch utilization that involves one transporter (Mal-II [PF1933 to PF1939]) and only three enzymes, amylopullulanase (PF1935*), 4-α-glucanotransferase (PF0272), and maltodextrin phosphorylase (PF1535). Their expression is upregulated on starch, and together they generate glucose and glucose-1-phosphate, which then feed into the novel glycolytic pathway of this organism. In addition, the results indicate that several hypothetical proteins encoded by three gene clusters are also involved in the transport and processing of α-glucan substrates by P. furiosus.}, number={6}, journal={JOURNAL OF BACTERIOLOGY}, author={Lee, HS and Shockley, KR and Schut, GJ and Conners, SB and Montero, CI and Johnson, MR and Chou, CJ and Bridger, SL and Wigner, N and Brehm, SD and et al.}, year={2006}, month={Mar}, pages={2115–2125} }
 @article{conners_montero_comfort_shockley_johnson_chhabra_kelly_2005, title={An expression-driven approach to the prediction of carbohydrate transport and utilization regulons in the hyperthermophilic bacterium Thermotoga maritima}, volume={187}, ISSN={["1098-5530"]}, DOI={10.1128/JB.187.21.7267-7282.2005}, abstractNote={ABSTRACT Comprehensive analysis of genome-wide expression patterns during growth of the hyperthermophilic bacterium Thermotoga maritima on 14 monosaccharide and polysaccharide substrates was undertaken with the goal of proposing carbohydrate specificities for transport systems and putative transcriptional regulators. Saccharide-induced regulons were predicted through the complementary use of comparative genomics, mixed-model analysis of genome-wide microarray expression data, and examination of upstream sequence patterns. The results indicate that T. maritima relies extensively on ABC transporters for carbohydrate uptake, many of which are likely controlled by local regulators responsive to either the transport substrate or a key metabolic degradation product. Roles in uptake of specific carbohydrates were suggested for members of the expanded Opp/Dpp family of ABC transporters. In this family, phylogenetic relationships among transport systems revealed patterns of possible duplication and divergence as a strategy for the evolution of new uptake capabilities. The presence of GC-rich hairpin sequences between substrate-binding proteins and other components of Opp/Dpp family transporters offers a possible explanation for differential regulation of transporter subunit genes. Numerous improvements to T. maritima genome annotations were proposed, including the identification of ABC transport systems originally annotated as oligopeptide transporters as candidate transporters for rhamnose, xylose, β-xylan, andβ -glucans and identification of genes likely to encode proteins missing from current annotations of the pentose phosphate pathway. Beyond the information obtained for T. maritima, the present study illustrates how expression-based strategies can be used for improving genome annotation in other microorganisms, especially those for which genetic systems are unavailable.}, number={21}, journal={JOURNAL OF BACTERIOLOGY}, author={Conners, SB and Montero, CI and Comfort, DA and Shockley, KR and Johnson, MR and Chhabra, SR and Kelly, RM}, year={2005}, month={Nov}, pages={7267–7282} }
 @article{shockley_scott_pysz_conners_johnson_montero_wolfinger_kelly_2005, title={Genorne-wide transcriptional variation within and between steady states for continuous growth of the hyperthermophile Thermotoga maritima}, volume={71}, ISSN={["1098-5336"]}, DOI={10.1128/AEM.71.9.5572-5576.2005}, abstractNote={ABSTRACT Maltose-limited, continuous growth of the hyperthermophile Thermotoga maritima at different temperatures and dilution rates (80°C/0.25 h−1, 80°C/0.17 h−1, and 85°C/0.25 h−1) showed that transcriptome-wide variation in gene expression within mechanical steady states was minimal compared to that between steady states, supporting the efficacy of chemostat-based approaches for functional genomics studies.}, number={9}, journal={APPLIED AND ENVIRONMENTAL MICROBIOLOGY}, author={Shockley, KR and Scott, KL and Pysz, MA and Conners, SB and Johnson, MR and Montero, CI and Wolfinger, RD and Kelly, RM}, year={2005}, month={Sep}, pages={5572–5576} }
 @article{johnson_montero_conners_shockley_bridger_kelly_2005, title={Population density-dependent regulation of exopolysaccharide formation in the hyperthermophilic bacterium Thermotoga maritima}, volume={55}, ISSN={["1365-2958"]}, DOI={10.1111/j.1365-2958.2004.04419.x}, abstractNote={Co‐cultivation of the hyperthermophiles Thermotoga maritima and Methanococcus jannaschii resulted in fivefold higher T. maritima cell densities when compared with monoculture as well as concomitant formation of exopolysaccharide and flocculation of heterotroph‐methanogen cellular aggregates. Transcriptional analysis of T. maritima cells from these aggregates using a whole genome cDNA microarray revealed the induction of a putative exopolysaccharide synthesis pathway, regulated by intracellular levels of cyclic diguanosine 3′,5′‐(cyclic)phosphate (cyclic di‐GMP) and mediated by the action of several GGDEF proteins, including a putative diguanylate cyclase (TM1163) and a putative phosphodiesterase (TM1184). Transcriptional analysis also showed that TM0504, which encodes a polypeptide containing a motif common to known peptide‐signalling molecules in mesophilic bacteria, was strongly upregulated in the co‐culture. Indeed, when a synthetically produced peptide based on TM0504 was dosed into the culture at ecologically relevant levels, the production of exopolysaccharide was induced at significantly lower cell densities than was observed in cultures lacking added peptide. In addition to identifying a pathway for polysaccharide formation in T. maritima, these results point to the existence of peptide‐based quorum sensing in hyperthermophilic bacteria and indicate that cellular communication should be considered as a component of the microbial ecology within hydrothermal habitats.}, number={3}, journal={MOLECULAR MICROBIOLOGY}, author={Johnson, MR and Montero, CI and Conners, SB and Shockley, KR and Bridger, SL and Kelly, RM}, year={2005}, month={Feb}, pages={664–674} }
 @article{johnson_montero_conners_shockley_pysz_kelly_2004, title={Functional genomics-based studies of the microbial ecology of hyperthermophilic micro-organisms}, volume={32}, ISSN={["1470-8752"]}, DOI={10.1042/BST0320188}, abstractNote={Although much attention has been paid to the genetic, biochemical and physiological aspects of individual hyperthermophiles, how these unique micro-organisms relate to each other and to their natural habitats must be addressed in order to develop a comprehensive understanding of life at high temperatures. Phylogenetic 16 S rRNA-based profiling of samples from various geothermal sites has provided insights into community structure, but this must be complemented with efforts to relate metabolic strategies to biotic and abiotic characteristics in high-temperature habitats. Described here are functional genomics-based approaches, using cDNA microarrays, to gain insight into how ecological features such as biofilm formation, species interaction, and possibly even gene transfer may occur in native environments, as well as to determine what genes or sets of genes may be tied to environmental functionality.}, number={2004 Apr}, journal={BIOCHEMICAL SOCIETY TRANSACTIONS}, author={Johnson, MR and Montero, CI and Conners, SB and Shockley, KR and Pysz, MA and Kelly, RM}, year={2004}, month={Apr}, pages={188–192} }
 @misc{pysz_conners_montero_shockley_johnson_ward_kelly_2004, title={Transcriptional analysis of biofilm formation processes in the anaerobic, hyperthermophilic bacterium Thermotoga maritima}, volume={70}, ISSN={["1098-5336"]}, DOI={10.1128/AEM.70.10.6098-6112.2004}, abstractNote={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 β-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 β-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.}, number={10}, journal={APPLIED AND ENVIRONMENTAL MICROBIOLOGY}, author={Pysz, MA and Conners, SB and Montero, CI and Shockley, KR and Johnson, MR and Ward, DE and Kelly, RA}, year={2004}, month={Oct}, pages={6098–6112} }
 @article{pysz_ward_shockley_montero_conners_johnson_kelly_2004, title={Transcriptional analysis of dynamic heat-shock response by the hyperthermophilic bacterium Thermotoga maritima}, volume={8}, ISSN={["1433-4909"]}, DOI={10.1007/s00792-004-0379-2}, number={3}, journal={EXTREMOPHILES}, author={Pysz, MA and Ward, DE and Shockley, KR and Montero, CI and Conners, SB and Johnson, MR and Kelly, RM}, year={2004}, month={Jun}, pages={209–217} }