Circular metagenome-assembled genome of Candidatus Patescibacteria recovered from anaerobic digestion sludge.

A single-contig, circular metagenome-assembled genome (cMAG) of Candidatus (Ca.) Patescibacteria was reconstructed from a mesophilic full-scale food waste treatment plant in Japan. The genome is of small size and lacks fundamental biosynthetic pathways. Taxonomic analysis using the Genome Taxonomy Database revealed that this cMAG belonged to the genus JAEZRQ01 (Ca. Parcubacteria).

Relationship Between Rumen Microbial Composition and Fibrolytic Isozyme Activity During the Biodegradation of Rice Straw Powder Using Rumen Fluid.

Rumen fibrolytic microorganisms have been used to increase the rate of lignocellulosic biomass biodegradation; however, the microbial and isozymatic characteristics of biodegradation remain unclear. Therefore, the present study investigated the relationship between rumen microorganisms and fibrolytic isozymes associated with lignocellulosic biomass hydrolysis. Rice straw, a widely available agricultural byproduct, was ground and used as a substrate. The biodegradation of rice straw powder was performed anaerobically in rumen fluid for 48 h. The results obtained revealed that 31.6 and 23.3% of cellulose and hemicellulose, respectively, were degraded. The total concentration of volatile fatty acids showed a 1.8-fold increase (from 85.4 to 151.6| |mM) in 48 h, and 1,230.1| |mL L-1 of CO2 and 523.5| |mL L-1 of CH4 were produced. The major isozymes identified by zymograms during the first 12| |h were 51- and 140-kDa carboxymethyl cellulases (CMCases) and 23- and 57-kDa xylanases. The band densities of 37-, 53-, and 58-kDa CMCases and 38-, 44-, and 130-kDa xylanases increased from 24 to 36 h. A microbial ana-lysis indicated that the relative abundances of Prevotella, Fibrobacter, and Bacteroidales RF16 bacteria, Neocallimastix and Cyllamyces fungi, and Dasytricha and Polyplastron protozoa were related to fibrolytic isozyme activity. The present results provide novel insights into the relationships between fibrolytic isozymes and rumen microorganisms during lignocellulose biodegradation.

Species-specific Primer and Probe Sets for Detection of Syntrophic Long-chain Fatty Acid-degrading Bacteria in Anaerobic Digestion Using Quantitative PCR.

Lipid-rich wastes are energy-dense substrates for anaerobic digestion. However, long-chain fatty acids (LCFAs), key intermediates in lipid degradation, inhibit methanogenic activity. In this study, TaqMan-based qPCR assays targeting the 16S rRNA gene of the cardinal LCFA-degrading bacterial species Syntrophomonas palmitatica and S. zehnderi were developed and validated. A trial experiment showed the advantage of species-specific quantification versus genus-specific quantification in assessing bacterial capacity for lipidic waste degradation. These qPCR assays will serve as monitoring tools for estimating the LCFA-degrading capacity of anaerobic digester communities and developing an effective strategy to enrich LCFA-degrading bacteria.

The role of atypical MAP kinase 4 in the host interaction with Cryptosporidium parvum.

Cryptosporidium parvum is an apicomplexan parasite that causes severe zoonotic diarrhea in humans and calves. Since there are no effective treatments or vaccines for infants or immunocompromised patients, it is important to understand the molecular mechanisms of the parasite-host interaction for novel drug discovery. Mitogen-activated protein kinase (MAP kinase) is a key host factor in interactions between host and various pathogens, including parasites. Although the function of conventional MAP kinases against parasite infection has been investigated, that of atypical MAP kinases remains largely unknown. Therefore, we focused on one of the atypical MAP kinases, MAPK4, and its effect on C. parvum infection in human intestinal cells. Here, we report that MAPK4-deficient intestinal cells showed a significant reduction in C. parvum infection. We also show that host MAPK4 has a role in host cell survival from C. parvum infection. In addition, we show that C. parvum requires host MAPK4 for its successful invasion and asexual reproduction. Taken together, our data suggest that MAPK4 is an important host factor contributing to C. parvum infection in human intestinal cells.

Exploration of microbial communities contributing to effective methane production from scum under anaerobic digestion.

Scum is formed by the adsorption of long-chain fatty acids (LCFAs) onto biomass surface in anaerobic digestion of oily substrates. Since scum is a recalcitrant substrate to be digested, it is disposed via landfilling or incineration, which results in biomass washout and a decrease in methane yield. The microbes contributing to scum degradation are unclear. This study aimed to investigate the cardinal microorganisms in anaerobic scum digestion. We pre-incubated a sludge with scum to enrich scum-degrading microbes. Using this sludge, a 1.3-times higher methane conversion rate (73%) and a faster LCFA degradation compared with control sludge were attained. Then, we analyzed the cardinal scum-degrading microbes in this pre-incubated sludge by changing the initial scum-loading rates. Increased 16S rRNA copy numbers for the syntrophic fatty-acid degrader Syntrophomonas and hydrogenotrophic methanogens were observed in scum high-loaded samples. 16S rRNA amplicon sequencing indicated that Syntrophomonas was the most abundant genus in all the samples. The amino-acid degrader Aminobacterium and hydrolytic genera such as Defluviitoga and Sporanaerobacter became more dominant as the scum-loading rate increased. Moreover, phylogenic analysis on Syntrophomonas revealed that Syntrophomonas palmitatica, which is capable of degrading LCFAs, related species became more dominant as the scum-loading rate increased. These results indicate that a variety of microorganisms that degrade LCFAs, proteins, and sugars are involved in effective scum degradation.