Isolation and Characterization of a Novel Equol-Producing Bacterium from Human Feces

An equol-producing bacterium was newly isolated from the feces of healthy humans and its morphological and biochemical properties were characterized. The cells were obligate anaerobes. They were non-sporulating, non-motile, gram-positive bacilliform bacteria with a pleomorphic morphology. The strain was catalase-positive, and oxidase-, urease-, and indole-negative. The only other sugar utilized by the strain was glycerin. The strain also degraded gelatin, but not esculin. It was most closely related to Eggerthella hongkongensis HKU10, with 93.3% 16S rDNA nucleotide sequence homology. Based on these features, the isolate was identified as a novel species of the genus Eggerthella. It was named Eggerthella sp. YY7918. Strain YY7918 converted substrates daidzein and dihydrodaidzein into S-equol, but did not convert daidzin, glysitein, genistein, or formononetin into it. An antimicrobial susceptibility assay indicated that strain YY7918 was susceptible to aminoglycoside-, tetracycline-, and new quinolone-antibiotics.     

Complete genomic sequence of the equol-producing bacterium Eggerthella sp. strain YY7918, isolated from adult human intestine

Eggerthella sp. strain YY7918 was isolated from the intestinal flora of a healthy human. It metabolizes daidzein (a soybean isoflavonoid) and produces S-equol, which has stronger estrogenic activities than daidzein. Here, we report the finished and annotated genomic sequence of this organism.     

Complete genome sequence of Eggerthella lenta type strain (IPP VPI 0255)

Eggerthella lenta (Eggerth 1935) Wade et al. 1999, emended Würdemann et al. 2009 is the type species of the genus Eggerthella, which belongs to the actinobacterial family Coriobacteriaceae. E. lenta is a Gram-positive, non-motile, non-sporulating pathogenic bacterium that can cause severe bacteremia. The strain described in this study has been isolated from a rectal tumor in 1935. Here we describe the features of this organism, together with the complete genome sequence, and annotation. This is the first complete genome sequence of the genus Eggerthella, and the 3,632,260 bp long single replicon genome with its 3123 protein-coding and 58 RNA genes is part of the Genomic Encyclopedia of Bacteria and Archaea project.     

An improved method of xylose utilization by recombinant Saccharomyces cerevisiae

The aim of this study was to develop a method to optimize expression levels of xylose-metabolizing enzymes to improve xylose utilization capacity of Saccharomyces cerevisiae. A xylose-utilizing recombinant S. cerevisiae strain YY2KL, able to express nicotinamide adenine dinucleotide phosphate, reduced (NADPH)-dependent xylose reductase (XR), nicotinamide adenine dinucleotide (NAD(+))-dependent xylitol dehydrogenase (XDH), and xylulokinase (XK), showed a low ethanol yield and sugar consumption rate. To optimize xylose utilization by YY2KL, a recombinant expression plasmid containing the XR gene was transformed and integrated into the aur1 site of YY2KL. Two recombinant expression plasmids containing an nicotinamide adenine dinucleotide phosphate (NADP(+))-dependent XDH mutant and XK genes were dually transformed and integrated into the 5S ribosomal DNA (rDNA) sites of YY2KL. This procedure allowed systematic construction of an S. cerevisiae library with different ratios of genes for xylose-metabolizing enzymes, and well-grown colonies with different xylose fermentation capacities could be further selected in yeast protein extract (YPX) medium (1?% yeast extract, 2?% peptone, and 2?% xylose). We successfully isolated a recombinant strain with a superior xylose fermentation capacity and designated it as strain YY5A. The xylose consumption rate for strain YY5A was estimated to be 2.32?g/gDCW/h (g xylose/g dry cell weight/h), which was 2.34 times higher than that for the parent strain YY2KL (0.99?g/gDCW/h). The ethanol yield was also enhanced 1.83 times by this novel method. Optimal ratio and expression levels of xylose-metabolizing enzymes are important for efficient conversion of xylose to ethanol. This study provides a novel method that allows rapid and effective selection of ratio-optimized xylose-utilizing yeast strains. This method may be applicable to other multienzyme systems in yeast.     

Rapid detection of human fecal Eubacterium species and related genera by nested PCR method

PCR procedures based on 16S rDNA gene sequence specific for seven Eubacterium spp. and Eggerthella lenta that predominate in the human intestinal tract were developed, and used for direct detection of these species in seven human feces samples. Three species of Eggerthella lenta, Eubacterium rectale, and Eubacterium eligens were detected from seven fecal samples. Eubacterium biforme was detected from six samples. It was reported that E. rectale, E. eligens, and E. biforme were difficult to detect by traditional culture method, but the nested PCR method is available for the detection of these species. This result shows that the nested PCR method utilizing a universal primer pair, followed by amplification with species-specific primers, would allow rapid detection of Eubacterium species in human feces.     

Bacterial conversion of secoisolariciresinol and anhydrosecoisolariciresinol

Aims:  It has been investigated whether secoisolariciresinol (SECO) and anhydrosecoisolariciresinol (AHS), an acid degradation product of SECO, could be fermented in a similar way, and to a similar extent, by members of the intestinal microbiota.
Methods and Results:  AHS and SECO were demethylated by Peptostreptococcus productus , Eubacterium limosum and Clostridium methoxybenzovorans . These bacteria have been identified as members of the human intestinal flora or closely related species. Demethylated AHS and demethylated SECO were purified by preparative RP-HPLC, and subsequently subjected to fermentation with Eggerthella lenta , Clostridium scindens and Clostridium hiranonis . Eggerthella lenta efficiently dehydroxylated demethylated SECO to enterodiol, whereas the other bacteria showed no dehydroxylation activity.
Conclusions:  The conversion of the diol structure of SECO into the furan ring in AHS did not influence the demethylation capability of the tested bacteria. The results also showed that the extent of dehydroxylation of demethylated AHS was much lower than that of demethylated SECO.
Significance and Impact of the Study:  Plant lignans are converted into bioactive mammalian lignans by the human intestinal bacteria. This study showed that the modification of plant lignans resulted in the formation a new type of mammalian lignan.     

A life table study on three genetic strains of Ophryotrocha diadema (Polychaeta,Dorvilleidae)

A life-table study was performed on three strains of Ophryotrocha diadema. The wild type strain, YY (yellow eggs), was compared with a recessive mutant strain, ww (white eggs), and the F₁, hybrid, Yw.

The viability of the YY strain was greater than that of the ww strain. The hybrids were intermediate. Expectation of life. e., of zygotes were: YY 27.9, Yw 19.1, and ww 15.1 wk, respectively. The total outcome of reproduction followed the same pattern; the net reproductive rates, R ₀, were related as 1:0.62:0.47 for YY: Yw: ww.

Reproduction began in the fourth week. A maximum reproductive output during the next 4 wk was followed by a fast decline. The intrinsic rate of natural increase, r, was 0.880 per week for the YY strain, 0.903 for the Yw strain and 0.872 for the ww strain. For all strains, the first 7 wk of reproduction contributed more than 99% of the Lotka equation σ e ^?rx l _x m _x = l, i.e., l _x m _x values at older ages would not substantially affect population growth. In this 7–wk period (and the previous nonreproductive weeks), mortality differences were small among strains. During the period of maximum reproduction the average size of egg masses was approximately the same in all strains. The heterozygote superiority was due to shorter intervals between successive spawnings.

It is suggested that in the opportunistic species O. diadema deviations from an r–selected reproductive pattern are due to small adult size and to its ancestry from a mainly K–selected, very old polychaete group.

O. diadema has proven to be a useful test animal for marine pollution research. Observed effects on survival and reproduction have been summarized in a model to demonstrate population consequences of sublethal pollutant levels.     

Functional metagenomics reveals novel salt tolerance loci from the human gut microbiome

Metagenomics is a powerful tool that allows for the culture-independent analysis of complex microbial communities. One of the most complex and dense microbial ecosystems known is that of the human distal colon, with cell densities reaching up to 10¹² per gram of faeces. With the majority of species as yet uncultured, there are an enormous number of novel genes awaiting discovery. In the current study, we conducted a functional screen of a metagenomic library of the human gut microbiota for potential salt-tolerant clones. Using transposon mutagenesis, three genes were identified from a single clone exhibiting high levels of identity to a species from the genus Collinsella (closest relative being Collinsella aerofaciens) (COLAER_01955, COLAER_01957 and COLAER_01981), a high G+C, Gram-positive member of the Actinobacteria commonly found in the human gut. The encoded proteins exhibit a strong similarity to GalE, MurB and MazG. Furthermore, pyrosequencing and bioinformatic analysis of two additional fosmid clones revealed the presence of an additional galE and mazG gene, with the highest level of genetic identity to Akkermansia muciniphila and Eggerthella sp. YY7918, respectively. Cloning and heterologous expression of the genes in the osmosensitive strain, Escherichia coli MKH13, resulted in increased salt tolerance of the transformed cells. It is hoped that the identification of atypical salt tolerance genes will help to further elucidate novel salt tolerance mechanisms, and will assist our increased understanding how resident bacteria cope with the osmolarity of the gastrointestinal tract.     

Notch 家族四个蛋白质在人胰腺癌细胞 HPAC 中对 YY1 和 EGFR水平的影响

Notch信号通路是肿瘤形成过程中一种重要的信号通路,其中心分子为Notch受体. Notch受体为细胞膜上的单次跨膜蛋白,介导细胞间信号转导,哺乳动物细胞内包括Notch1、Notch2、Notch3和Notch4的4个成员. Notch家族4个蛋白质在结构和功能上存在差异.前期研究显示,Notch1信号通路与转录因子YY1（YING-YANG 1）、表皮生长因子受体（EGFR）间存在调控作用. 本研究在人胰腺癌细胞HPAC中,采用RNA干扰技术,分别降低细胞中Notch家族4个蛋白质的表达,检测YY1和EGFR在mRNA和蛋白质水平上的表达;并构建相应的激活形式的Notch受体--Notch胞内结构域（Notch intracellular domain,NICD）真核表达质粒,在HPAC细胞中分别过表达4种NICD,检测其对YY1和EGFR表达水平的影响. 结果显示,降低细胞中Notch1或Notch3的表达,均使HPAC细胞中EGFR mRNA和蛋白质水平升高（P<0.05）,而降低Notch2和Notch4后,EGFR mRNA和蛋白质水平没有改变（P>0.05）.分别降低4个Notch的表达,对YY1的蛋白质和mRNA表达水平均没有改变（P>0.05）. 在HPAC细胞中过表达N1ICD和N3ICD后,YY1和EGFR的蛋白质水平降低（P<0.05）,而过表达N2ICD和N4ICD后,YY1和EGFR蛋白质水平没有改变（P>0.05）.分别过表达4种NICD均没有改变YY1和EGFR的mRNA表达水平（P>0.05）.初步得出结论是,在HPAC细胞中,Notch信号通路经Notch1和Notch3影响EGFR的表达. Notch1和Notch3对EGFR的表达可能具有负调控作用. 在Notch1和Notch3过度激活时,这种调控作用通过YY1介导. 本文可为深入研究Notch信号通路对胰腺癌发生发展的作用机制提供有意义的参考.     

Peptide YY stimulates the expression of apolipoprotein A-IV gene in Caco-2 intestinal cells

The effect of peptide YY, a gastrointestinal hormone, on the expression of the apolipoprotein A-IV gene in the intestinal epithelial cell line Caco-2 was examined by semiquantitative RT-PCR followed by Southern hybridization with an inner oligonucleotide probe. Apolipoprotein A-IV mRNA levels were increased in response to peptide YY in a dose- and time-dependent fashion. Western blotting revealed that the exogenous peptide YY increased the intracellular concentration of apolipoprotein A-IV. In contrast, apolipoprotein A-I, B, and C-III mRNA did not respond to peptide YY. Differentiated Caco-2 cells expressed Y1- but not Y2- and Y5-receptor subtype mRNA. The present results suggest that peptide YY modulates apolipoprotein A-IV gene expression, likely via the Y1-receptor subtype in intestinal epithelial cells.