This study aimed to evaluate the composition of the gastric microbiota in the gastric mucosa and gastric fluid of patients with chronic antral gastritis. Specifically, we sought to determine whether Helicobacter pylori (Hp) infection changes the bacterial community in the gastric mucosa or alters the microbiota in the gastric fluid. The bacterial community at another site in the stomach was also investigated. DNA was extracted from 160 samples collected from 40 patients with chronic antral gastritis (20 Hp-positive and 20 Hp-negative cases). Three tissue samples of the gastric mucosa (gastric angle, body, and antral mucosa) and one tube of gastric fluid were collected from every patient. A 16S rRNA amplification library was created, and high-throughput sequencing was performed. A profile of the community composition was obtained using bioinformatics methods, including cluster, taxonomy, and diversity analyses. Analysis of the gastric bacterial community revealed that the community compositions of the gastric mucosa and gastric fluid of patients without Hp are similar to but show differences from those of Hp-positive patients. The microbiota in Hp-positive patients exhibited reduced microbial diversity, and the gastric fluid of these patients contained a small proportion of Hp. The richness of Leptotrichia in mucosal samples was greater than that in gastric fluid samples from Hp-negative patients with chronic antral gastritis. Hp changes the growth of other microbiota in the mucosa and affects the microbiota in the gastric fluid of patients with chronic antral gastritis. In addition to Hp, the presence of other bacteria might be related to the development of chronic antral gastritis.
L-Pipecolic acid is utilized as a vital component of specific chemical compounds, such as immunosuppressive drugs, anticancer reagents, and anesthetic reagents. We isolated and characterized a novel L-aminoacylase, N-acetyl-L-pipecolic acid-specific aminoacylase (LpipACY), from Pseudomonas sp. AK2. The subunit molecular mass of LpipACY was 45 kDa and was assumed to be a homooctamer in solution. The enzyme exhibited high substrate specificity toward N-acetyl-L-pipecolic acid and a high activity for N-acetyl-L-pipecolic acid and N-acetyl-L-proline. This enzyme was stable at a high temperature (60°C for 10 min) and under an alkaline pH (6.0–11.5). The N-terminal and internal amino acid sequences of the purified enzyme were STTANTLILRNG and IMASGGV, respectively. These sequences are highly consistent with those of uncharacterized proteins from Pseudomonas species, such as amidohydrolase and peptidase. We also cloned and overexpressed the gene coding LpipACY in Escherichia coli. Moreover, the recombinant LpipACY exhibited properties similar to native enzyme. Our results suggest that LpipACY is a potential enzyme for the enzymatic synthesis of L-pipecolic acid. This study provides the first description of the enzymatic characterization of L-pipecolic acid specific amino acid acylase.
We clarified the roles of VPH1 in Cryptococcus neoformans serotype D by examining the detailed phenotypes of VPH1-deficient cells (Δvph1) in terms of their capability to grow in acidic and alkaline pH, at a high temperature, and under high osmotic conditions, in addition to the involvement of VPH1 in copper (Cu) homeostasis and the expression of some C. neoformans virulence factors. Δvph1 could grow well on minimal medium (YNB) but exhibited hypersensitivity to 20 μM Cu due to the failure to induce Cu-detoxifying metallothionein genes (CMT1 and CMT2). In contrast, Δvph1 exhibited defective growth on rich medium (YPD), and the induction of Cu transporter genes (CTR1 and CTR4) did not occur in this medium, implying that this strain was incapable of the uptake of Cu ions for growth. However, the addition of excess Cu promoted CTR gene expression and supported Δvph1 growth. These results suggested that the lack of the VPH1 gene disturbed Cu homeostasis in C. neoformans. Moreover, the loss of Vph1 function influenced the urease activity of C. neoformans.
A unicellular cyanobacterium that produces a large amount of exopolysaccharide (EPS) was isolated. The isolate, named Chroococcus sp. FPU101, grew between 20 and 30°C and at light intensities between 10 and 80 μmol m–2 s–1. Purified EPS from Chroococcus sp. FPU101 had a molecular size of 5.9 × 103 kDa and contained galactose, rhamnose, fucose, xylose, mannose, glucose, galacturonic acid, and glucuronic acid at a molar ratio of 17.2:15.9:14.1:11.0:9.6:9.5:13.0:9.7. The EPS content significantly increased when the NaCl concentration in the medium was increased from 1.7 to 100 mM. However, high NaCl concentrations did not significantly affect the molecular size or chemical composition of the EPS. The genes wza, wzb, wzc, wzx, wzy, and wzz that are involved in EPS synthesis were conserved in the genome of Chroococcus sp. FPU101, which was sequenced in this study. These results suggest that the Wzy-dependent pathway is potentially involved in EPS production in this organism.
Pressed sake cake, a by-product of sake brewing, is a rich dietary source of folates, which are important vitamins for humans. However, considerable losses of folates occur during storage and cooking. We have previously reported that Km67, the house sake yeast strain of Kiku-masamune sake brewery, can accumulate high folate levels. In this study, we found that the folate content of pressed sake cakes produced with Km67 remained at approximately their maximum level after the fermentation activity stopped. To elucidate the mechanisms of high folate accumulation in Km67, we analyzed the expression of 23 folate-metabolizing genes. The expression of ABZ1 and FOL3 was almost always higher in Km67 than in Kyokai no. 701 yeast (K701), which suggested that enhanced expression of the genes involved in folate biosynthesis was a mechanism of high folate accumulation in Km67. We found that the folates of Km67 pressed sake cakes were quantitatively stable at 4°C under refrigerated storage conditions. In addition, the homocysteine content of Km67 pressed sake cakes was almost always higher than that of K701 pressed sake cakes. This result suggests that a reason for high folate accumulation in Km67 yeast is the need to reduce the intracellular concentration of homocysteine. Our results provide biologically meaningful information on folate metabolism in yeast.
Strains of Lactococcus lactis subsp. cremoris are used to produce yogurt containing exopolysaccharides with a sticky texture. When strain G3-2 producing exopolysaccharides was grown at elevated temperatures, a spontaneous mutant EPSC, which had lost exopolysaccharides biosynthesis, was isolated. Genomes of the two strains were determined to be composed of a 2.4-Mb chromosome and up to eleven plasmids, and it was revealed that one of the plasmids encoding the gene cluster for exopolysaccharides biosynthesis was lost selectively in EPSC.