This paper describes the cloning, purification, and characterization of thioredoxin (Trx) and thioredoxin reductase (TrxR) and the structure determination of TrxR from the ionizing radiation-tolerant bacterium Deinococcus radiodurans strain R1. The genes from D. radiodurans encoding Trx and TrxR were amplified by PCR, inserted into a pET expression vector, and overexpressed in Escherichia coli. The overexpressed proteins were purified by metal affinity chromatography, and their activity was demonstrated using well-established assays of insulin precipitation (for Trx), 5,5-dithiobis(2-nitrobenzoic acid) (DTNB) reduction, and insulin reduction (for TrxR). In addition, the crystal structure of oxidized TrxR was determined at 1.9-Å resolution. The overall structure was found to be very similar to that of E. coli

Lactic acid bacteria (LAB) contamination of beer presents a continual economic threat to brewers. Interestingly, only certain isolates of LAB can grow in the hostile beer environment (e.g., as studied here, Lactobacillus brevis BSO 464 (Lb464) and a non-ropy isolate of Pediococcus claussenii ATCC BAA-344(T) (Pc344NR)), indicating that significant genetic specialization is required. The genes hitA, horA, horB, horC, and bsrA, which have been proposed to confer beer-spoiling ability to an organism, are suspected of counteracting the antimicrobial effects of hops. However, these genes are not present in the same combination (if at all) across beer-spoiling organisms. As such, we sought to investigate the extent to which these genes participate during Lb464 and Pc344NR mid-logarithmic growth in beer through reverse transcription quantitative PCR analysis. We first determined the optimal reference gene set needed for data normalization and, for each bacterium, established that two genes were needed for accurate assessment of gene expression. Following this, we found that horA expression was induced for Pc344NR, but not for Lb464, during growth in beer. Instead, horC expression was dramatically increased in Lb464 when growing in beer, whereas no change was detected for the other putative beer-spoilage-related genes. This indicates that HorC may be one of the principle mediators enabling growth of Lb464 in beer, whereas in Pc344NR, this may be attributable to HorA. These findings not only reveal that Lb464 and Pc344NR are unique in their beer-specific genetic expression profile but also indicate that a range of genetic specialization exists among beer-spoilage bacteria.

BackgroundThere are many programs available for generating simulated whole-genome shotgun sequence reads. The data generated by many of these programs follow predefined models, which limits their use to the authors' original intentions. For example, many models assume that read lengths follow a uniform or normal distribution. Other programs generate models from actual sequencing data, but are limited to reads from single-genome studies. To our knowledge, there are no programs that allow a user to generate simulated data following non-parametric read-length distributions and quality profiles based on empirically-derived information from metagenomics sequencing data.ResultsWe present BEAR (Better Emulation for Artificial Reads), a program that uses a machine-learning approach to generate reads with lengths and quality values that closely match empirically-derived distributions. BEAR can emulate reads from various sequencing platforms, including Illumina, 454, and Ion Torrent. BEAR requires minimal user input, as it automatically determines appropriate parameter settings from user-supplied data. BEAR also uses a unique method for deriving run-specific error rates, and extracts useful statistics from the metagenomic data itself, such as quality-error models. Many existing simulators are specific to a particular sequencing technology; however, BEAR is not restricted in this way. Because of its flexibility, BEAR is particularly useful for emulating the behaviour of technologies like Ion Torrent, for which no dedicated sequencing simulators are currently available. BEAR is also the first metagenomic sequencing simulator program that automates the process of generating abundances, which can be an arduous task.ConclusionsBEAR is useful for evaluating data processing tools in genomics. It has many advantages over existing comparable software, such as generating more realistic reads and being independent of sequencing technology, and has features particularly useful for metagenomics work.

Growth of specific lactic acid bacteria in beer leads to spoiled product and economic loss for the brewing industry. Microbial growth is typically inhibited by the combined stresses found in beer (e.g., ethanol, hops, low pH, minimal nutrients); however, certain bacteria have adapted to grow in this harsh environment. Considering little is known about the mechanisms used by bacteria to grow in and spoil beer, transcriptome sequencing was performed on a variant of the beer-spoilage organism Pediococcus claussenii ATCC BAA-344T (Pc344-358). Illumina sequencing was used to compare the transcript levels in Pc344-358 growing mid-exponentially in beer to those in nutrient-rich MRS broth. Various operons demonstrated high gene expression in beer, several of which are involved in nutrient acquisition and overcoming the inhibitory effects of hop compounds. As well, genes functioning in cell membrane modification and biosynthesis demonstrated significantly higher transcript levels in Pc344-358 growing in beer. Three plasmids had the majority of their genes showing increased transcript levels in beer, whereas the two cryptic plasmids showed slightly decreased gene expression. Follow-up analysis of plasmid copy number in both growth environments revealed similar trends, where more copies of the three non-cryptic plasmids were found in Pc344-358 growing in beer. Transcriptome sequencing also enabled the addition of several genes to the P . claussenii ATCC BAA-344T genome annotation, some of which are putatively transcribed as non-coding RNAs. The sequencing results not only provide the first transcriptome description of a beer-spoilage organism while growing in beer, but they also highlight several targets for future exploration, including genes that may have a role in the general stress response of lactic acid bacteria.

Specific isolates of lactic acid bacteria (LAB) can grow in the harsh beer environment, thus posing a threat to brew quality and the economic success of breweries worldwide. Plasmid-localized genes, such as horA, horC, and hitA, have been suggested to confer hop tolerance, a trait required for LAB survival in beer. The presence and expression of these genes among LAB, however, do not universally correlate with the ability to grow in beer. Genome sequencing of the virulent beer spoilage organism Lactobacillus brevis BSO 464 revealed the presence of eight plasmids, with plasmids 1, 2, and 3 containing horA, horC, and hitA, respectively. To investigate the roles that these and the other five plasmids play in L. brevis BSO 464 growth in beer, plasmid curing with novobiocin was used to derive 10 plasmid variants. Multiplex PCRs were utilized to determine the presence or absence of each plasmid, and how plasmid loss affected hop tolerance and growth in degassed (noncarbonated) beer was assessed. Loss of three of the eight plasmids was found to affect hop tolerance and growth in beer. Loss of plasmid 2 (horC and 28 other genes) had the most dramatic effect, with loss of plasmid 4 (120 genes) and plasmid 8 (47 genes) having significant, but smaller, impacts. These results support the contention that genes on mobile genetic elements are essential for bacterial growth in beer and that beer spoilage ability is not dependent solely on the three previously described hop tolerance genes or on the chromosome of a beer spoilage LAB isolate. Beer is a very harsh environment for bacterial growth due to unique physiochemical attributes. Specifically, the presence of antimicrobial hop compounds (15 to 55 ppm iso-␣-acids) and ethanol (0.5 to 14% [vol/vol]) (1), coupled with the low availability of nutrients, a microaerophilic environment, low pH, and, finally, pressure in the packaged product due to CO 2 content, together mean that contaminating microorganisms must employ compensatory mechanisms to survive in the milieu. When successful microbial growth in beer does occur, the result is a spoiled product with unappealing off flavors and an altered sensory profile, ultimately leading to issues with brand confidence and economic loss for brewers globally (2).Isolated beer-spoiling organisms (BSOs) frequently belong to the genus Lactobacillus or Pediococcus, both of which are classified as lactic acid bacteria (LAB) (3, 4). The ability to spoil beer, however, is not intrinsic to all members of a given species in each genus and is instead isolate specific. This indicates that BSOs have undergone a degree of genetic specialization relative to non-BSO LAB isolates of the same genus and species. LAB are a diverse group of organisms, and a given species can be isolated from a number of environments. For example, Lactobacillus plantarum isolates can be found, not only in spoiled beer, but also in spoiled meats and the human intestinal microbiome (5). Due to the varied nature of these environments and the frequency with which specific bacteri...