Journal of General and Applied Microbiology最新文献

In Saccharomyces cerevisiae, ethyl caprylate is produced by the esterification of caprylic acid, which is synthesized through the action of fatty acid synthase. A recent study reported a yeast mutant with a single nucleotide substitution in the alpha subunit of fatty acid synthase (FAS2) gene (F1279Y; 3836T>A) that produced large amounts of ethyl caprylate. Here, we designed two primer sets (P1/P2 and P3/P4) with mismatches that incorporate restriction sites for the enzymes NdeI and SspI, respectively and developed an easy and rapid polymerase chain reaction-restriction fragment length polymorphism assay to identify yeasts harboring the FAS2-F1279Y mutation associated with high ethyl caprylate productivity.

As a central signaling molecule, c-di-GMP (bis-(3,5)-cyclic diguanosine monophosphate) is becoming the focus for research in bacteria physiology. Pseudomonas aeruginosa PAO1 genome contains highly complicated c-di-GMP metabolizing genes and a number of these proteins have been identified and investigated. Especially, a sophisticated network of these proteins is emerging. In current study, mainly through Bacteria-2-Hybrid assay, we found PA0575 (RmcA), a GGDEF-EAL dual protein, to interact with two other dual proteins of PA4601 (MorA) and PA4959 (FimX). These observations imply the intricacy of c-di-GMP metabolizing protein interactions. Our work thus provides one piece of data to increase the understandings to c-di-GMP signaling.

The decolorization of 11 dyes by granular sludge from an anaerobic expanded granular sludge bed (EGSB) reactor was evaluated. Biological decolorization of Reactive Red 21, 23, and 180, and Reactive Yellow 15, 17, and 23 in model textile wastewater was observed for the first time after a 7-day incubation (over 94% decolorization). According to the sequencing analysis of 16S rRNA gene amplicons from EGSB granular sludge, the operational taxonomic unit related to Paludibacter propionicigenes showed the highest increase in relative abundance ratios in the presence of dyes (7.12 times on average over 11 dyes) compared to those without dyes.

Consumption of temperature-abused marine fish containing elevated levels of histamine results in histamine poisoning. Histamine is a biogenic amine produced in fish by the action of certain groups of bacteria which are capable of producing an exogenous enzyme called histidine decarboxylase (HDC). Morganella morganii is one of the major causative organisms of histamine poisoning. In this study, the histamine forming potential of M. morganii (BSS142) was evaluated when it was co-incubated with proteolytic as well as polyamine forming bacteria. This experiment was designed to examine whether biotic factors such as proteolysis and the presence of other amines influenced histamine forming ability of BSS142. The study showed that the proteolytic activity of Aeromonas hydrophila as well as Pseudomonas aeruginosa greatly enhanced the histamine forming ability of M. morganii. Psychrobacter sangunis, a non proteolytic polyamine producer, negatively influenced histamine production by M. morganii.

Godo is a traditional fermented soy food made in Aomori prefecture, Japan. It is mainly made of soybeans, rice koji, and salt. Since godo ripens during the long and severe winter in northeast Japan, it is assumed that lactic acid bacteria inhabiting godo have cold tolerance. We aimed to investigate the presence or absence of psychrotrophic lactic acid bacteria in godo. The viable counts of estimated lactic acid bacteria ranged from 10⁶ to 10⁸ cfu/g. In addition, aerobic and anaerobic microorganisms were detected in four godo products though the microbial population differed from sample to sample. Twenty-two bacterial strains were able to be isolated from godo, and all of the isolated strains were Gram-positive and catalase-negative. Some of the isolates grew well at 10°C. The carbohydrate fermentation profile of the selected three strains was determined by API50 CHL analysis. These strains were identified as Leuconostoc mesenteroides, and Latilactobacillus sakei by 16S rRNA gene sequence analysis. Leuconostoc mesenteroides strains HIT231 and HIT252, and Latilactobacillus sakei strain HIT273 could grow at 5°C in MRS broth, but their optimum growth temperature was 20°C-30°C. These results suggest that psychrotrophic lactic acid bacteria presumed to be derived from rice koji are present in godo, which is one of the factors in the low temperature ripening of godo in winter.

The present study investigated the efficacy of bacterial cellulose production by K. xylinus TISTR 1011 and K. nataicola TISTR 975 using yam bean juice as a nutrient source, and the physicochemical and sensory characteristics of bacterial cellulose were examined. Bacterial cellulose content, production yield, and production rate were significantly higher when K. xylinus TISTR 1011 rather than K. nataicola TISTR 975 was used as the bacterial strain. The analysis of physicochemical characteristics revealed that bacterial cellulose produced by K. xylinus TISTR 1011 using yam bean juice medium had higher scores for CIE L*, a*, and b* values, wet weight, moisture content, firmness, and gel strength than bacterial cellulose produced by K. nataicola TISTR 975. In contrast, sensory evaluation showed that the acceptability scores and preference of all attributes of bacterial cellulose produced by K. nataicola TISTR 975 using yam bean juice medium were higher than those of bacterial cellulose produced by K. xylinus TISTR 1011. The results of this study indicate that yam bean juice from yam bean tubers, an alternative raw material agricultural product, can be used as a nutrient source for producing bacterial cellulose or nata by Komagataeibacter strains.

Bacteriocins are a large family of peptides synthesized ribosomally by a variety of bacterial species. The genome of one of the thermophilic Gram-positive bacteria, Aeribacillus pallidus PI8, was found to possess an operon comprising five genes possibly involved in the production of a putative bacteriocin that was named pcnABCDE for the production of "pallidocyclicin." This study investigated the function of the pcn operon experimentally. The heterologous expression of the entire pcn operon from the plasmid was toxic to Escherichia coli but not to Bacillus subtilis. However, when the entire pcn operon was expressed constitutively, even the growth of B. subtilis was impaired, and at least pcnA was implied to serve as the precursor of pallidocyclicin. In addition, a strain of B. subtilis expressing the entire pcn operon from the plasmid showed toxicity to another thermophilic species, Geobacillus kaustophilus, at elevated temperatures, whereas another strain lacking pcnE alone from the pcn operon lost the toxicity, suggesting that pcnE might be involved in the biosynthesis of pallidocyclicin when it is produced in B. subtilis.

During the making of rice-koji for sake production, 2,4,6-trichlorophenol (TCP) is O-methylated to 2,4,6-trichloroanisole (TCA) by the koji-mold, Aspergillus oryzae, resulting in a musty/moldy off-odor, which significantly reduces the quality of sake. Thus, we aim to develop A. oryzae strains with a less-efficient ability to produce TCA. TCP is a fungicide that suppresses the growth of fungi, whereas TCA does not. The exact effects of TCP on the growth of A. oryzae are unknown. However, it is assumed that a strain with low TCP conversion ability will be sensitive to TCP concentration. In this study, we investigated the effects of the different concentrations of TCP on the growth suppression of A. oryzae. As the TCP concentration in the media increased, the growth rate, and conidia formation of A. oryzae slowed down. No growth was observed in liquid culture (for 1 day at 30°C) containing more than 30 μg/mL of TCP and in agar culture (for 7 days at 30°C) containing more than 50 μg/mL of TCP. However, A. oryzae was able to grow on alpha rice containing higher concentrations of TCP. The results in agar culture are consistent with the effects of TCP on other Aspergillus species.

In this study, two fibrous carbon anodes (namely, pleated non-woven graphite (PNWG) and carbon brush (CB) made from artificial carbon) and bamboo charcoal (BC) were evaluated for current recovery from sewage wastewater. When these anodes were polarized at 0.2 V vs. Ag/AgCl in sewage wastewater, CB produced a maximum current of 2.9 A/m². This exceeded that produced by PNWG (1.5 A/m²) and BC (1.4 A/m²). The accumulative charge recovery achieved with CB was superior to those achieved with the other two (1.6- and 2.2-fold higher than that with PNWG and BC, respectively). During the cyclic voltammetry analysis, CB demonstrated the highest catalytic current with maximum potential in the range of -0.6 to 0.4 V vs. Ag/AgCl and the smallest anode resistance (0.20 Ωm²). Direct cell counting revealed that the fibrous anodes (CB and PNWG) attached most of the cells in the anodes (80%), whereas BC did not. In contrast, the proportion of Geobacter species, a representative electrogenic microorganism in the total bacteria, was observed to be similar among the three anodes (4.4-5.8%). The tubular microbial fuel cell (ø 5.0 cm) equipped with an air-chamber core wrapped with an anion exchange membrane (AEM) and the CB delivered a current of 1.8 A/m². This is higher than those reported in the existing literature for the same microbial fuel cell (MFC) configuration. This indicates that the alteration of the anode from planar to brush can contribute toward improving the current recovery through the air-cathode-AEM-MFC. The BC needs improvement to have more specific surface area, whereas it showed superiority in cost efficiency considering material and processing.