Reduction of Escherichia coli O157:H7 in Biofilms Using Bacteriophage BPECO 19 : Phage control <i>E. coli</i> O157:H7 in biofilms…

Sadekuzzaman, Mohammad,Yang, Sungdae,Mizan, Md. Furkanur Rahaman,Ha, Sang-Do Wiley Blackwell (Blackwell Publishing) 2017 Journal of Food Science Vol.82 No.6

A novel calcium-independent phospholipase A₂ and its physiological roles in development and immunity of a lepidopteran insect, <i>Spodoptera exigua</i>

Sadekuzzaman, Md.,Gautam, Neelam,Kim, Yonggyun PERGAMON 2017 DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY Vol. No.

<P><B>Abstract</B></P> <P>Phospholipase A<SUB>2</SUB> (PLA<SUB>2</SUB>) catalyzes hydrolysis of ester linkage at <I>sn-2</I> position of phospholipids. At least 15 groups (I-XV) of PLA<SUB>2</SUB> gene superfamily are associated with various physiological processes such as digestion, secretion, immunity, and maintenance of membrane integrity. This study suggests that various insects encode putative Group VI PLA<SUB>2</SUB>s representing intracellular and calcium-independent PLA<SUB>2</SUB>s (iPLA<SUB>2</SUB>). These insect iPLA<SUB>2</SUB>s are separated into at least two subgroups: iPLA<SUB>2</SUB>A (Group VIA-like) and iPLA<SUB>2</SUB>B (non-Group VIA). Most insects encode genes of iPLA<SUB>2</SUB>B type, although their biological functions are currently unknown. This study predicted a novel iPLA<SUB>2</SUB> from <I>Spodoptera exigua</I> (a lepidopteran insect) (SeiPLA<SUB>2</SUB>B) and analyzed its physiological functions by RNA interference (RNAi). <I>SeiPLA</I> <SUB> <I>2</I> </SUB> <I>B</I> encodes 336 amino acid sequence with a predicted size of about 36.6 kDa and an isoelectric point at pH 8.61. It possesses a lipase catalytic site, but does not have ankyrin repeats in the amino terminal region. Phylogenetic analysis indicated that <I>SeiPLA</I> <SUB> <I>2</I> </SUB> <I>B</I> was clustered with other Group VI iPLA<SUB>2</SUB>s, in which <I>SeiPLA</I> <SUB> <I>2</I> </SUB> <I>B</I> was closely associated with Group VIF gene while <I>SeiPLA</I> <SUB> <I>2</I> </SUB> <I>A</I> was closely related to Group VIA gene. <I>SeiPLA</I> <SUB> <I>2</I> </SUB> <I>B</I> was expressed in all developmental stages of <I>S. exigua</I>. In larval stage, <I>SeiPLA</I> <SUB> <I>2</I> </SUB> <I>B</I> was expressed in fat body, hemocyte, and epidermis, but not in digestive tract. <I>SeiPLA</I> <SUB> <I>2</I> </SUB> <I>B</I> RNAi significantly reduced PLA<SUB>2</SUB> enzyme activities and resulted in developmental retardation and immunosuppression. Though RNAi treatment did not significantly change fatty acid composition in fat body lipids, it significantly increased lipid peroxidation. Taken together, our results suggest that SeiPLA<SUB>2</SUB>B plays important roles in the development and immunity of <I>S. exigua.</I> </P> <P><B>Highlights</B></P> <P> <UL> <LI> A novel intracellular and calcium-independent PLA<SUB>2</SUB> (SeiPLA<SUB>2</SUB>B) gene is predicted. </LI> <LI> Its RNA interference caused oxidative damage by increasing lipid peroxidation. </LI> <LI> SeiPLA<SUB>2</SUB>B plays roles in development and immunity. </LI> </UL> </P>

Specific inhibition of <i>Xenorhabdus hominickii</i>, an entomopathogenic bacterium, against different types of host insect phospholipase A₂

Sadekuzzaman, Md.,Kim, Yonggyun Elsevier 2017 Journal of invertebrate pathology Vol.149 No.-

<P><B>Abstract</B></P> <P>Phospholipase A<SUB>2</SUB> (PLA<SUB>2</SUB>) hydrolyzes ester bond of phospholipids at the <I>sn-2</I> position to release free fatty acid and lysophospholipids. Some PLA<SUB>2</SUB>s preferentially release arachidonic acid which is subsequently oxygenated into eicosanoids to mediate immune responses in insects. <I>Xenorhabdus hominickii</I> is an entomopathogenic bacterium that can suppress insect immunity by inhibiting PLA<SUB>2</SUB> activity. However, little is known about target PLA<SUB>2</SUB> types inhibited by <I>X. hominickii.</I> Therefore, the objective of this study was to determine PLA<SUB>2</SUB> types in the host insect, <I>Spodoptera exigua</I> using specific inhibitors. All developmental stages of <I>S. exigua</I> possessed significant PLA<SUB>2</SUB> activities, with late larval stages showing relatively higher PLA<SUB>2</SUB> activities. In different larval tissues, hemocytes had higher PLA<SUB>2</SUB> activities than fat body, gut, or epidermis. Various developmental and tissue extracts exhibited differential susceptibilities to three different PLA<SUB>2</SUB> inhibitors. Late larva-to-adult stages were highly susceptible to all three different types of PLA<SUB>2</SUB> inhibitors. In contrast, extracts from egg and young larval stages were not susceptible to secretory PLA<SUB>2</SUB> (sPLA<SUB>2</SUB>) or calcium-independent cellular PLA<SUB>2</SUB> (iPLA<SUB>2</SUB>) inhibitors, although they were susceptible to a calcium-dependent cellular PLA<SUB>2</SUB> (cPLA<SUB>2</SUB>) inhibitor in a dose-dependent manner. Different tissues of fifth instars exhibited variation in susceptibility to inhibitors, with epidermal tissue being sensitive to cPLA<SUB>2</SUB> inhibitor only while other tissues were sensitive to all three types of inhibitors. Bacterial challenge with heat-killed <I>X. hominickii</I> significantly increased PLA<SUB>2</SUB> activity. However, live bacteria suppressed the induction of PLA<SUB>2</SUB> activity. An organic extract of <I>X. hominickii</I>-culture broth inhibited the susceptibility of <I>S. exigua</I> to sPLA<SUB>2</SUB>- and iPLA<SUB>2</SUB>- specific inhibitors, but not to cPLA<SUB>2</SUB>-specific inhibitor. Oxindole, a component of the organic extract, exhibited an inhibitory pattern similar to the organic extract. Taken together, our results indicate that <I>S. exigua</I> possesses different PLA<SUB>2</SUB> types and that <I>X. hominickii</I> can inhibit PLA<SUB>2</SUB>s susceptible to sPLA<SUB>2</SUB>- and iPLA<SUB>2</SUB>- specific inhibitors<I>.</I> </P> <P><B>Highlights</B></P> <P> <UL> <LI> <I>Xenorhabdus hominickii</I> exhibits entomopathogenicity by inhibiting host PLA<SUB>2</SUB>. </LI> <LI> There are at least three different PLA<SUB>2</SUB>s in the host insect, <I>Spodoptera exigua</I>. </LI> <LI> <I>X. hominickii</I> inhibits sPLA<SUB>2</SUB> or iPLA<SUB>2</SUB> with its secondary metabolite(s). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Application of bacteriophages for the inactivation of <i>Salmonella</i> spp. in biofilms

Sadekuzzaman, Mohammad,Mizan, Md. Furkanur Rahaman,Yang, Sungdae,Kim, Hyung-Suk,Ha, Sang-Do SAGE Publications 2018 Food science and technology international Vol.24 No.5

Effectiveness of a phage cocktail as a biocontrol agent against <i>L. monocytogenes</i> biofilms

Sadekuzzaman, Mohammad,Yang, Sungdae,Mizan, Md. Furkanur Rahaman,Kim, Hyung-Suk,Ha, Sang-Do Elsevier 2017 FOOD CONTROL Vol.78 No.-

<P>Listeria monocytogenes can persist and form biofilms in a food environment which are difficult to eradicate because biofilms are inherently resistant to a variety of antimicrobial treatments. Therefore, alternative approaches such as bacteriophages have been suggested as a promising biocontrol agent against biofilms. The aim of this study was to evaluate the efficacy of a cocktail bacteriophage product (ListShield (TM)) against L. monocytogenes biofilms. These biofilms were established on lettuce, stainless steel, rubber, and a MBEC biofilm device and exposed to the ListShield (TM) phage preparation (1 x 10(8) PFU/mL) for 2 h. ListShield (TM) had sufficient potency to significantly reduce the biofilm (P < 0.05) in all cases. Biofilm reduction achieved after ListShield (TM) treatment on the stainless steel coupon was 1.9-2.4 log CFU/cm(2) and on the rubber surface approximately 1.0 log CFU/cm(2). Phage application on lettuce inactivated biofilm bacteria up to 0.7 log CFU/cm(2). These results suggest that bacteriophage preparation ListShield (TM) is an effective tool for the inactivation of L. monocytogenes biofilms in the food industry. (C) 2016 Elsevier Ltd. All rights reserved.</P>

Activity of thyme and tea tree essential oils against selected foodborne pathogens in biofilms on abiotic surfaces

Sadekuzzaman, Mohammad,Mizan, Md Furkanur Rahaman,Kim, Hyung-Suk,Yang, Sungdae,Ha, Sang-Do Elsevier 2018 FOOD SCIENCE AND TECHNOLOGY -ZURICH- Vol.89 No.-

<P>Owing to their preservative and antimicrobial effects, essential oils (EOs) are promising natural ingredients for the food industry. The main objective of this study was to investigate the activity of thyme and tea tree oils against selected foodborne pathogens in biofilm mode. The major compounds of these EOs were analyzed by gas chromatography-mass spectrometry (GC-MS) and their antimicrobial activity was determined by a standard broth dilution assay. Biofilms were formed by Escherichia coli 0157:117, Listeria monocytogenes, and Salmonella spp. on abiotic surfaces and were treated with EOs at the minimum inhibitory concentration (MIC) and 0.1% (v/v) for 2 h. Our results demonstrate that EO treatment reduced biofilm cells up to 3.5 log CFU/cm(2), 2.1 log CFU/cm(2), and 2.5 log CFU/peg on stainless steel (SS), rubber, and minimum biofilm eradication concentration (MBEC (TM)) surfaces, respectively. Structural changes of the biofilm after exposure to EOs was confirmed by field emission scanning electron microscopy and viability of biofilm cells was observed using a confocal laser scanning microscope. Overall, these results suggest that EOs could be used to reduce foodborne pathogens in biofilms.</P>

Humoral immunity mediated by nitric oxide and crosstalk with eicosanoids

Md. Sadekuzzaman,Yonggyun Kim 한국응용곤충학회 2017 한국응용곤충학회 학술대회논문집 Vol.2017 No.10

Nitiric oxide (NO) and eicosanoids function as crucial immune mediators in insects. This study focuses on cross-talkbetween two immune mediators in term of humoral immune response in Spodoptera exigua. Up-regulation of eight differentanti-microbial peptides (AMP) was observed against bacterial challenge. In contrast, injection of E. coli along with L-NAMEsignificantly down regulation the AMP production whereas D-NAME was not effective. The injection of E. coli withdexamethasone or SNAP also decreased AMP production whereas arachidonic acid (AA) compensated the dexamethasoneeffects. RNA inerferece against SeNOS showed the down-regulation of defensin mRNA level, whereas dsNOS injectionswith AA reversed the gene regulation.

Host range of Steinernema monticolum and immunosuppressive activity by Xenorhabdus hominickii against Spodoptera exigua

Md. Sadekuzzaman,Youngjin Park,Yonggyun Kim 한국응용곤충학회 2016 한국응용곤충학회 학술대회논문집 Vol.2016 No.04

Entomopathogenic nematodes (EPNs) of the genus Steinernema are pathogenic to the insects and well known as ideal models for understanding parasite-host interaction. EPNs harbor a number of bacterial symbionts in their gut belonging to the noble genus Xenorhabdus which are capable of killing insects by themselves or by combination with nematodes by suppressing insect immune defense. Here, we report host range of Steinernema monticolum and its symbiont Xenorhabdus hominickii. S. monticolum has a diverse host range including lepidopteran and coleopteran insects although they showed higher pathogenicity to the lepidopteran insects. Especially, X. hominickii suppressed insect immune responses. A target insect, Spodoptera exigua, exhibited both cellular and humoral immune responses by expressing antimicrobial peptides and forming nodules in response to heat-killed X. hominickii. However, live bacteria significantly suppressed the immune responses. An addition of arachidonic acid to the bacterial infection significantly rescued the immune responses, suggesting eicosanoid biosynthetic pathway as a pathogenic target of X. hominickii.

RNA interference of nitric oxide synthase expression suppresses PLA2 activation in response to bacterial challenge

Md Sadekuzzaman,Yonggyun Kim 한국응용곤충학회 2017 한국응용곤충학회 학술대회논문집 Vol.2017 No.04

Nitric oxide (NO) is an immune mediator in several insects. In addition, eicosanoids mediate various immune responses in response to microbial challenges. This study focuses on cross-talk between two immune mediators. Nitric oxide synthase (SeNOS) of Spodoptera exigua was predicted in its cDNA sequence by interrogation to the transcriptomes and validated by RT-PCR against developmental stage and larval tissues. RNA interference (RNAi) of SeNOS suppressed nodule formation of S. exigua larvae against heat-killed Xenorhabdus hominickii. RNAi of SeNOS also suppressed NO levels in fat body and hemocytes along with suppression of PLA2 activity. NOS-specific inhibitor, L-NAME, also inhibited PLA2 activity, but its enantiomer, D-NAME, did not. However, PLA2 of dexamethasone or oxindole did not suppress NO levels in the immune tissues. In addition, X hominickii did not inhibit up-regulation of NO levels. These results suggest that NO signal activates PLA2 to produce eicosanoids to mediate immune responses

Expression and enzyme activities of two PLA2s in Spodoptera exigua

Md Sadekuzzaman,Yonggyun Kim 한국응용곤충학회 2016 한국응용곤충학회 학술대회논문집 Vol.2016 No.10

Phospholipase A2 (PLA2) catalyzes the committed step for eicosanoid biosynthesis. Two cellular PLA2 genes (iPLA2 and cPLA2) have been identified in Spodoptera exigua. PLA2 activity varied among developmental stages and different tissues. There was a positive correlation between PLA2 activities and their expression levels. Interestingly, there was significant inhibition by sPLA2 inhibitor, suggesting a presence of sPLA2 in S. exigua. An entomopathogenic bacterium, Xenorhabdus hominickii, infection suppressed expression of PLA2 genes and its extract inhibited enzyme activities. Oxindole of a bacterial metabolite of X. hominikii inhibited PLA2 activity and expression.