A novel gene-diet interaction promotes organismal lifespan and host protection during infection via the mitochondrial UPR.

Cells use a variety of mechanisms to maintain optimal mitochondrial function including the mitochondrial unfolded protein response (UPRmt). The UPRmt mitigates mitochondrial dysfunction by differentially regulating mitoprotective gene expression through the transcription factor ATFS-1. Since UPRmt activation is commensurate with organismal benefits such as extended lifespan and host protection during infection, we sought to identify pathways that promote its stimulation. Using unbiased forward genetics screening, we isolated novel mutant alleles that could activate the UPRmt. Interestingly, we identified one reduction of function mutant allele (osa3) in the mitochondrial ribosomal gene mrpl-2 that activated the UPRmt in a diet-dependent manner. We find that mrpl-2(osa3) mutants lived longer and survived better during pathogen infection depending on the diet they were fed. A diet containing low levels of vitamin B12 could activate the UPRmt in mrpl-2(osa3) animals. Also, we find that the vitamin B12-dependent enzyme methionine synthase intersects with mrpl-2(osa3) to activate the UPRmt and confer animal lifespan extension at the level of ATFS-1. Thus, we present a novel gene-diet pairing that promotes animal longevity that is mediated by the UPRmt.

A pathogen branched-chain amino acid catabolic pathway subverts host survival by impairing energy metabolism and the mitochondrial UPR.

The mitochondrial unfolded protein response (UPRmt) is a stress-activated pathway promoting mitochondrial recovery and defense against infection. In C. elegans, the UPRmt is activated during infection with the pathogen Pseudomonas aeruginosa-but only transiently. As this may reflect a pathogenic strategy to target a pathway required for host survival, we conducted a P. aeruginosa genetic screen to uncover mechanisms associated with this temporary activation. Here, we find that loss of the P. aeruginosa acyl-CoA dehydrogenase FadE2 prolongs UPRmt activity and extends host survival. FadE2 shows substrate preferences for the coenzyme A intermediates produced during the breakdown of the branched-chain amino acids valine and leucine. Our data suggests that during infection, FadE2 restricts the supply of these catabolites to the host hindering host energy metabolism in addition to the UPRmt. Thus, a metabolic pathway in P. aeruginosa contributes to pathogenesis during infection through manipulation of host energy status and mitochondrial stress signaling potential.

Enhanced Bioethanol Production from Potato Peel Waste Via Consolidated Bioprocessing with Statistically Optimized Medium.

In this study, an extensive screening was undertaken to isolate some amylolytic microorganisms capable of producing bioethanol from starchy biomass through Consolidated Bioprocessing (CBP). A total of 28 amylolytic microorganisms were isolated, from which 5 isolates were selected based on high α-amylase and glucoamylase activities and identified as Candida wangnamkhiaoensis, Hyphopichia pseudoburtonii (2 isolates), Wickerhamia sp., and Streptomyces drozdowiczii based on 26S rDNA and 16S rDNA sequencing. Wickerhamia sp. showed the highest ethanol production (30.4 g/L) with fermentation yield of 0.3 g ethanol/g starch. Then, a low cost starchy waste, potato peel waste (PPW) was used as a carbon source to produce ethanol by Wickerhamia sp. Finally, in order to obtain maximum ethanol production from PPW, a fermentation medium was statistically designed. The effect of various medium ingredients was evaluated initially by Plackett-Burman design (PBD), where malt extracts, tryptone, and KH2PO4 showed significantly positive effect (p value < 0.05). Using Response Surface Modeling (RSM), 40 g/L (dry basis) PPW and 25 g/L malt extract were found optimum and yielded 21.7 g/L ethanol. This study strongly suggests Wickerhamia sp. as a promising candidate for bioethanol production from starchy biomass, in particular, PPW through CBP.

Microbial diversity changes with rhizosphere and hydrocarbons in contrasting soils.

In the ecotoxicological assessment of petroleum hydrocarbon-contaminated soil, microbial community profile is important aspect due to their involvement in soil functions. However, soil physicochemical properties and the inhabiting plants could dictate the microbial composition. A question remains unanswered is, how an integrated approach may be utilized to account for various contrasting soil properties, plant types (reference vs. native) and the nature of the hydrocarbon contamination. In this study, we utilized bacterial DNA profiling techniques to investigate the relationship between soil properties, contaminant and plant species. Results identified that Proteobacteria and Actinobacteria were the most abundant bacteria of the 45 phyla identified in the hydrocarbon-contaminated soil. The bulk and rhizosphere microbiome showed that the contaminated soil originally had quite distinct bacterial communities compared to the artificially contaminated soil (mine soil = 95 genera vs. other soils = 2-29 genera). In these cases, not significantly but the native plant slightly increased bacterial diversity and relative abundance in the same soils. Also, within each site, the bacterial community was significantly altered with the hydrocarbon concentration. In this instance, the influence of the contaminant was strong and also with the soil pH and organic matter. These results would significantly contribute to the novel insights on the molecular technique-based hydrocarbon toxicity assessment and the development of the further integrative approach with other microbial community and their metabolic profile in the contaminated sites.

Market Assessment and Product Evaluation of Probiotic Containing Dietary Supplements Available in Bangladesh Market.

Probiotics containing food supplements available in Bangladesh market were identified and collected for assessment. To assess their label claim, they were resuspended into sterile distilled water. Then, series dilutions of each sample solution were prepared and immediately plated out, in duplicate, into De Man Rogosa Sharpe (MRS) agar. These plates were then incubated at 37°C for 48 hours and colonies were counted. Viable cell numbers stated on the labels were compared with actual viable cell numbers. To assess the viability of the probiotics included in the products, probiotic strains were isolated from each of the four products and screened for inhibitory activity against six indicator strains. It was surprisingly found that although the viable cell numbers of all supplements were three to four log cycles lower than label claim of the products, however, this problem did not affect the inhibitory activity of the probiotic strains against indicator strains according to in vitro assessment. Legislation and regulation regarding prebiotic-probiotic containing products should be built up in Bangladesh to ensure quality products supply to the consumers. Moreover, manufacturers of probiotic containing products should take the responsibility for providing the consumer with scientifically and legally correct information.

Understanding the mechanism of heat stress tolerance caused by high trehalose accumulation in Saccharomyces cerevisiae using DNA microarray.

DNA microarray analysis was performed to examine the stress tolerance mechanism of a Saccharomyces cerevisiae recombinant strain exhibiting high trehalose accumulation and heat stress tolerance. Results suggest that the upregulation of sugar transporter genes is one of the key events for heat stress tolerance of the recombinant strain.

Differential importance of trehalose accumulation in Saccharomyces cerevisiae in response to various environmental stresses.

Trehalose is believed to play an important role in stress tolerance in the yeast Saccharomyces cerevisiae. In this research, the responses to various environmental stresses, such as high ethanol concentration, heat, oxidative, and freezing stresses, were investigated in a strain with deletion of the NTH1, NTH2, and ATH1 genes encoding trehalases that are involved in trehalose degradation and the triple deletion strains overexpressing TPS1 or TPS2, both of which encode trehalose biosynthesis enzymes in S. cerevisiae. The contents of trehalose constitutively accumulated in the TPS1- and TPS2-overexpressing triple deletion strains were higher than that in the original triple deletion strain. High trehalose accumulation and growth activity were observed in the TPS2-overexpressing triple deletion strain after ethanol stress induction. The same was also observed in the triple deletion and the TPS1- and TPS2-overexpressing triple deletion strains after heat stress induction. In case of freezing stress, all the recombinant strains with high constitutive trehalose content showed high tolerance. However, in case of oxidative stress, trehalose accumulation could not make the yeast cells tolerant. Our results indicated that high trehalose accumulation can make yeast cells resistant to multiple stresses, but the importance of this accumulation before or after stress induction is varied depending on the type of stress.

Effect of trehalose accumulation on response to saline stress in Saccharomyces cerevisiae.

To examine the effect of trehalose accumulation on response to saline stress in Saccharomyces cerevisiae, we constructed deletion strains of all combinations of the trehalase genes ATH1, NTH1 and NTH2 and examined their growth behaviour and intracellular trehalose accumulation under non-stress and saline-stress conditions. Saline stress was induced in yeast cells by NaCl addition at the exponential growth phase. All deletion strains showed similar specific growth rates and trehalose accumulation to their parent strain under non-stress conditions. However, under the saline stress condition, one single deletion strain, nth1Delta, two double deletion strains, nth1Delta ath1Delta and nth1Delta nth2Delta, and the triple deletion strain nth1Deltanth2Delta ath1Delta, all of which carry the nth1Delta deletion, showed increased trehalose accumulation as compared to the parent and other deletion strains. In particular, our statistical analysis revealed that the triple deletion strain showed a higher growth rate under the saline stress condition than the parent strain. Moreover, some deletion strains showed further trehalose accumulation under non-stress conditions by overexpression of the TPS1 or TPS2 genes encoding the enzymes related to trehalose biosynthesis at the mid-exponential phase. Such increased trehalose accumulation prior to NaCl addition could improve the growth of these strains under saline stress. Our results indicate that high trehalose accumulation prior to NaCl addition, rather than after NaCl addition, is necessary to achieve high growth activity under stress conditions.