Prolonged exposure to simulated microgravity diminishes dendritic cell immunogenicity.

Immune dysfunction due to microgravity remains a hurdle in the next step of human space exploration. Dendritic cells (DC) represent a critical component of immunity, given their role in the detection of invaders and the subsequent task of activating T cells to respond and eliminate the threat. Upon encounter with microbes, DC undergo a process of maturation, whereby the cells upregulate the expression of surface proteins and secrete cytokines, both required for the optimal activation of CD4+ and CD8+ T cells. In this study, DC were cultured from 2-14 days in a rotary cell culture system, which generates a simulated microgravity (SMG) environment, and then the cells were assessed for maturation status and the capacity to activate T cells. Short-term culture (<72 h) of DC in SMG resulted in an increased expression of surface proteins associated with maturation and interleukin-6 production. Subsequently, the SMG exposed DC were superior to Static control DC at activating both CD4+ and CD8+ T cells as measured by interleukin-2 and interferon-γ production, respectively. However, long-term culture (4-14 d) of DC in SMG reduced the expression of maturation markers and the capacity to activate T cells as compared to Static DC controls.

Sensitization of gram-negative and gram-positive bacteria to jenseniin G by sublethal injury.

Jenseniin G, a bacteriocin produced by Propionibacterium thoenii P126, is active against related propionibacteria and some lactic acid bacteria and is sporostatic to botulinal spores. The objective of this study was to evaluate the effects of sublethal stress on jenseniin G activity. Bacillus cereus, Enterococcus faecalis, Escherichia coli, Listeria monocytogenes, Salmonella Typhimurium, Shigella flexneri, Staphylococcus aureus, and Yersinia enterocolitica were subjected to temperature, acid, and osmotic stresses in the presence of jenseniin G. The bacteriocin reduced the viability of sublethally injured cultures, although the extent of reduction varied with strain and treatment. E. faecalis was the most sensitive to temperature stress; no reduction of viable counts occurred in the absence of jenseniin G, and a 1.5-log reduction occurred in the presence of jenseniin G. B. cereus, L. monocytogenes, and S. aureus were more sensitive to jenseniin G when exposed to heat stress than when exposed to cold stress, whereas E. coli, Salmonella Typhimurium, and S. flexneri were more sensitive to jenseniin G when exposed to cold stress than when exposed to heat stress. When comparing an acid stress test alone to a combination of acid stress and jenseniin G, E. faecalis and L. monocytogenes showed the greatest sensitivities with 4.87- and 2.82-log reductions, respectively, after 7 days. All cultures except for S. aureus were adversely affected by the combination of salt stress and jenseniin G. Salmonella Typhimurium showed the greatest sensitivity to salt stress with jenseniin G (a 1.54-log reduction at day 7) when compared to salt stress alone (a 0.55-log reduction at day 7). Jenseniin G, like bacteriocins produced by other gram-positive species, has broader activity against stressed organisms.

Organization of carboxysome genes in the thiobacilli.

The order of genes in the carboxysome gene clusters of four thiobacilli was examined and the possibility of the cluster forming an operon evaluated. Furthermore, carboxysome peptide homologs were compared with respect to similarities in primary sequence, and the unique structural features of the shell protein CsoS2 were described.

Two Copies of form I RuBisCO genes in Acidithiobacillus ferrooxidans ATCC 23270.

Acidithiobacillus ferrooxidans ATCC 23270 possesses two copies of form I ribulose bisphosphate carboxylase/oxygenase (RuBisCO). The nucleotide sequence identity between the two large and two small subunit peptides was 75% and 58%, respectively. It is proposed that the two copies resulted from lateral gene transfer.