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RISS 인기검색어
- 검색키워드
- 저자 : Siti Nurjanah (검색결과 5 건)
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Stability and Growth Characteristics of GFPuv- Labeled Cronobacter sakazakii Isolated from Foods
Siti Nurjanah,Ratih Dewanti-Hariyadi,Sri Estuningsih,Maggy Thenawidjaja Suhartono 한국식품과학회 2014 Food Science and Biotechnology Vol.23 No.5
Stability of ultraviolet green fluorescent protein(GFPuv)-labeled Cronobacter sakazakii and C. muytjensiiisolated from foods and the effects of the plasmid GFPuv(pGFPuv) on growth were analyzed. PCR analysis andmicroscopic observation showed that C. sakazakii and C. muytjensii isolates took up the plasmid into cells andexpressed the GFPuv gene. All Cronobacter transformantsmaintained this plasmid after frozen storage and 2consecutive subcultures. The C. sakazakii FWHd16transformant was the most stable, while the C. muytjensiiFWHd11 transformant was the least stable. All transformantsshowed nearly identical growth curves during lag, log andstationary phases, compared to wild type parental isolates. The maximum bacterial growth rates (μmax) of thetransformants and parents were similar, indicating that thepresence of pGFPuv in transformants did not affect cellgrowth. Stable GFPuv-labeled Cronobacter has potentialfor use in tracking bacterial behavior during food handlingand drying.
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Maryam Jameelah,Ratih Dewanti-Hariyadi,Siti Nurjanah 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.3
Cronobacter spp. in powdered infant formula has been etiologically linked to meningitis and necrotizing enterocolitis in certain groups of infants. This study aimed to determine whether C. sakazakii Yrt2a strain experiencing desiccation stress could enter viable but nonculturable (VBNC) state as well as to examine the expression of genes associated with stress and virulence during the above states. Stress and VBNC conditions were determined based on viability and culturability assays. Expression of genes related to stress (rpoS) and virulence (hfq and ompA) was evaluated by real-time PCR. The results showed that C. sakazakii Yrt2a entered VBNC 24 days post exposure to 2 h of desiccation treatment. The expression of rpoS, hfq and ompA genes was up-regulated during stress conditions, suggesting that Cronobacter successfully managed stress to maintain its culturability while maintaining its virulence. The expression of the target genes decreased at VBNC state but remained higher than that of a normal state. These findings reinforce the assumption that C. sakazakii undergoing VBNC state maintains its pathogenicity.
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Jameelah, Maryam,Dewanti-Hariyadi, Ratih,Nurjanah, Siti 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.3
Cronobacter spp. in powdered infant formula has been etiologically linked to meningitis and necrotizing enterocolitis in certain groups of infants. This study aimed to determine whether C. sakazakii Yrt2a strain experiencing desiccation stress could enter viable but nonculturable (VBNC) state as well as to examine the expression of genes associated with stress and virulence during the above states. Stress and VBNC conditions were determined based on viability and culturability assays. Expression of genes related to stress (rpoS) and virulence (hfq and ompA) was evaluated by real-time PCR. The results showed that C. sakazakii Yrt2a entered VBNC 24 days post exposure to 2 h of desiccation treatment. The expression of rpoS, hfq and ompA genes was up-regulated during stress conditions, suggesting that Cronobacter successfully managed stress to maintain its culturability while maintaining its virulence. The expression of the target genes decreased at VBNC state but remained higher than that of a normal state. These findings reinforce the assumption that C. sakazakii undergoing VBNC state maintains its pathogenicity.
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Maerani Maerani,Ratih Dewanti-Hariyadi,Siti Nurjanah 한국식품과학회 2020 Food Science and Biotechnology Vol.29 No.9
This research aimed to evaluate the effect of acidstress on the expression of stress regulator (grxB and rpoS)and virulence (ompA, hfq, and cpa) genes of Cronobactersakazakii Yrt2a. The results showed that C. sakazakii Yrt2aexperienced decrease in number during acid stress and wasno longer culturable 90 min post exposure to pH 3.0. During acid stress, the expression of grxB, rpoS, ompA, cpaand hfq was upregulated by 2.15; 2.19; 1.55; 1.1 and 1.41log, respectively. However, all genes expression wasdownregulated when the bacteria entered the unculturablestate. The expression of gene grxB, rpoS, ompA, cpadecreased to 1.04; 0.37; 0.84 and 1.71 log, respectively;while hfq gene expression reached a level lower than thatof control. This research implies a supposition that duringacid stress, C. sakazakii was capable of maintaining itsculturability and pathogenicity until they are no longerculturable.
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Fenny Amilia Mahara,Lilis Nuraida,Hanifah Nuryani Lioe,Siti Nurjanah 한국식품영양과학회 2023 Preventive Nutrition and Food Science Vol.28 No.4
Folate (vitamin B9) is an essential nutrient for cell metabolism, especially in pregnant women; however, folate deficiency is a major global health issue. To address this issue, folate-rich fermented foods have been used as alternative sources of natural folate. Lactic acid bacteria (LAB), which are commonly involved in food fermentation, can synthesize and excrete folate into the medium, thereby increasing folate levels. However, screening for folate-producing LAB strains is necessary because this ability is highly dependent on the bacterial strain. Some strains of LAB consume folate, and their presence in a fermentation mix can lower the folate levels of the final product. Since microorganisms efficiently regulate folate biosynthesis to meet their growth needs, some strains of folate-producing LAB can deplete folate levels if folate is available in the media. Such folate-efficient producers possess a feedback inhibition mechanism that downregulates folate biosynthesis. Therefore, the application of folate-overproducing strains may be a key strategy for increasing folate levels in media with or without available folate. Many studies have been conducted to screen folate-producing bacteria, but very few have focused on the identification of overproducers. This is probably because of the limited understanding of the regulation of folate biosynthesis in LAB. In this review, we discuss the roles of folate-biosynthetic genes and their contributions to the ability of LAB to synthesize and regulate folate. In addition, we present various hypotheses regarding the regulation of the feedback inhibition mechanism of folate-biosynthetic enzymes and discuss strategies for obtaining folate-overproducing LAB strains.
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