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Several permanently cold solar system bodies are being investigated with regard to their potential habitability, including Mars and icy moons. In such locations, microbial life would have to cope with low temperatures and both high and low pressures, ranging from ∼102 to 103 Pa on the surface of Mars to upward of ∼108-109 Pa in the subsurface oceans of icy moons. The bacterial genus Carnobacterium consists of species that were previously shown to be capable of growth in the absence of oxygen at low temperatures and at either low pressure or high pressure, but to date the entire pressure range of the genus has not been explored. In the present study, we subjected 14 Carnobacterium strains representing 11 species to cultivation in a complex liquid medium under anaerobic conditions at 2°C and at a range of pressures spanning 5 orders of magnitude, from 103 to 107 Pa. Eleven of the 14 strains showed measurable growth rates at all pressures tested, representing the first demonstration of terrestrial life forms capable of growth under such a wide range of pressures. These findings expand the physical boundaries of the capabilities of life to occur in extreme extraterrestrial environments.

Despite their ubiquity and their involvement in food spoilage, the genus Carnobacterium remains rather sparsely characterized at the genome level. Carnobacterium inhibens K1(T) is a member of the Carnobacteriaceae family within the class Bacilli. This strain is a Gram-positive, rod-shaped bacterium isolated from the intestine of an Atlantic salmon. The present study determined the genome sequence and annotation of Carnobacterium inhibens K1(T). The genome comprised 2,748,608 bp with a G + C content of 34.85 %, which included 2621 protein-coding genes and 116 RNA genes. The strain contained five contigs corresponding to presumptive plasmids of sizes: 19,036; 24,250; 26,581; 65,272; and 65,904 bp.

We used microarrays to identify the causes of sporulation deficiencies in Bacillus subtilis after 6,000 generations of evolution. We found that sporulation loss did not result from large-scale deletions; therefore, it must have resulted from smaller indels and/or substitutions. Transcription patterns of one strain versus its ancestor showed that sporulation was not initiated and suggested that sporulation loss may be part of an overall decline in plasticity.

The role of DNA repair by nonhomologous end joining (NHEJ), homologous recombination, spore photoproduct lyase, and DNA polymerase I and genome protection via [alpha]/[beta]-type small, acid-soluble spore proteins (SASP) in Bacillus subtilis spore resistance to accelerated heavy ions (high-energy charged [HZE] particles) and X rays has been studied. Spores deficient in NHEJ and [alpha]/[beta]-type SASP were significantly more sensitive to HZE particle bombardment and X-ray irradiation than were the recA, polA, and splB mutant and wild-type spores, indicating that NHEJ provides an eflicient DNA double-strand break repair pathway during spore germination and that the loss of the [alpha]/[beta]-type SASP leads to a significant radiosensitivity to ionizing radiation, suggesting the essential function of these spore proteins as protectants of spore DNA against ionizing radiation.

RNA polymerase is a central macromolecular machine controlling the flow of information from genotype to phenotype, and insights into global transcriptional regulation can be gained by studying mutational perturbations in the enzyme. Mutations in the RNA polymerase [beta] subunit gene rpoB causing resistance to rifampin ([Rif.sup.r]) in Bacillus subtilis were previously shown to lead to alterations in the expression of a number of global phenotypes known to be under transcriptional control, such as growth, competence for transformation, sporulation, and germination (H. Maughan, B. Galeano, and W. L. Nicholson, J. Bacteriol. 186:2481-2486, 2004). To better understand the global etfects of rpoB mutations on metabolism, wild-type and 11 distinct congenic [Rif.sup.r] mutant strains of B. subtilis were tested for utilization of 95 substrates by use of Biolog GP2 MicroPlates. A number of alterations of substrate utilization patterns were observed in the [Rif.sup.r] mutants, including the utilization of novel substrates previously unknown in B. subtilis, such as gentiobiose, [beta]-methylD-glucoside, and D-psicose. The resuits indicate that combining global metabolic profiling with mutations in RNA polymerase provides a system-wide approach for uncovering previously unknown metabolic capabilities and further understanding global transcriptional control circuitry in B. subtilis.

Phenotypic loss is an important evolutionary force in nature but the mechanism (s) responsible for loss remains unclear. We used both simulation and multiple-regression approaches to analyze data on the loss of sporulation, a complex bacterial developmental process, during experimental evolution of Bacillus subtilis. Neutral processes of mutational degradation alone were sufficient to explain loss-of-sporulation ability in four of five populations, while evidence that selection facilitated mutational loss was found for only one population. These results are discussed in the context of the evolution of sporulation in particular and phenotypic loss in general.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.06.014 Byline: Andrew C. Schuerger (a), Wayne L. Nicholson (b) Keywords: Mars; Astrobiology Abstract: Robotic spacecraft are launched with finite levels of terrestrial microorganisms that are similar to the microbial communities within facilities in which spacecraft are assembled. In particular, spores of mesophilic aerobic Bacillus species are common spacecraft contaminants considered most likely to survive interplanetary transfer to Mars. During the cruise phase to Mars, and then again during surface operations, microbial bioloads are exposed to a diversity of biocidal factors that are likely to render the microbial species either dead or significantly inhibited from active metabolic activity and replication. We report here, for the first time, that interactive effects of low pressure, low temperature, and high CO.sub.2 atmospheres approaching conditions likely to be encountered on the martian surface strongly inhibit the growth and replication of seven common Bacillus spp. isolated from spacecraft. Tests were conducted within a small glass bell-jar system maintained in a low-temperature microbial incubator. Atmospheric pressures were controlled at 1013 (Earth-normal), 100, 50, 35, 25, or 15 mb, and temperatures were maintained at 30, 20, 15, 10, or 5a[degrees]C. Experiments were carried out for 48 h or 7 days under either Earth-normal O.sub.2/N.sub.2 or pure CO.sub.2 atmospheres. Results indicated that low pressure, low temperature, and high CO.sub.2 atmospheres, applied separately or in combination, were capable of inhibiting the growth and replication of B. pumilus SAFR-032, B. pumilus FO-36B, B. subtilis HA-101, B. subtilis 42HS-1, B. megaterium KL-197, B. licheniformis KL-196, and B. nealsonii FO-092 under simulated martian conditions. Endospores of all seven Bacillus spp. strains failed to germinate and grow at 25 mb at 30a[degrees]C. Although, vegetative cells of these strains exhibited a slightly greater ability to replicate at lower pressures than did endospores, vegetative cells of these species failed to grow at pressures below 25 mb. Interactive effects of these environmental parameters acted to generally increase the inhibitory nature of the low-pressure conditions on growth and replication of the seven Bacillus spp. tested. Author Affiliation: (a) Department of Plant Pathology, University of Florida, Bldg. M6-1025, Space Life Sciences Lab, Kennedy Space Center, FL 32899, USA (b) Department of Microbiology and Cell Science, University of Florida, Bldg. M6-1025, Space Life Sciences Lab, Kennedy Space Center, FL 32899, USA Article History: Received 15 December 2005; Revised 20 June 2006

An experimental evolution system having two different environments that were used for addressing the population genetic cause of trait loss all along evolutionary time is described. Results reveal that growth in prototrophy was lost in all populations regardless of the experimental environment, in one environment the pattern of trait loss was due to selection and in the other environment the cause remains inconclusive.