scholarly journals Distinct Nitrite and Nitric Oxide Physiologies inEscherichia coliandShewanella oneidensis

2018 ◽  
Vol 84 (12) ◽  
pp. e00559-18 ◽  
Author(s):  
Qiu Meng ◽  
Jianhua Yin ◽  
Miao Jin ◽  
Haichun Gao
Keyword(s):  
Nitric Oxide ◽  
Escherichia Coli ◽  
Growth Inhibition ◽  
Shewanella Oneidensis ◽  
Food Preservation ◽  
Content Type ◽  
E Coli ◽  
Cell Extracts ◽  
Copper Oxidase

ABSTRACTNitrite has been used as a bacteriostatic agent for centuries in food preservation. It is widely accepted that this biologically inert molecule functions indirectly, serving as a stable reservoir of bioactive nitric oxide (NO) and other reactive nitrogen species to impact physiology. As a result, to date, we know surprisingly little aboutin vivotargets of nitrite. Here, we carry out comparative analyses of nitrite and NO physiology inEscherichia coliand inShewanella oneidensis, a Gram-negative environmental bacterium renowned for respiratory versatility. These two bacteria differ from each other in many aspects of nitrite and NO physiology, including NO generation, NO degradation, and unexpectedly, their contrary susceptibility to nitrite and NO. In cell extracts of both bacteria, most of the NO targets are also susceptible to nitrite, and vice versa. However, with respect to growth inhibition caused by NO, the targets are impacted distinctly; NO targets are responsible for the inhibition of growth ofE. colibut not ofS. oneidensis. More surprisingly, all proteins identified to be implicated in NO tolerance in other bacteria appear to play a dispensable role in protectingS. oneidensisagainst NO. These data suggest thatS. oneidensisis equipped with a robust but yet unknown NO protecting system. In the case of nitrite, it is clear that the target of physiological significance in both bacteria is cytochrome heme-copper oxidase.IMPORTANCENitrite is toxic to living organisms at high levels, but such antibacterial effects of nitrite are attributable to the formation of nitric oxide (NO), a highly reactive radical gas molecule. Here, we report thatShewanella oneidensisis highly resistant to NO but sensitive to nitrite compared toEscherichia coliby approximately 4-fold. In both bacteria, nitrite inhibits bacterial growth by targeting cytochrome heme-copper oxidase. In contrast, the targets of NO are diverse. Although these targets are similar inE. coliandS. oneidensis, they are responsible for growth inhibition caused by NO in the former but not in the latter. Overall, the presented data, along with the previous data, solidify a proposal that thein vivotargets of NO and nitrite in bacteria are largely different.

scholarly journals Isolation of a Gene Responsible for the Oxidation oftrans-Anethole topara-Anisaldehyde by Pseudomonas putida JYR-1 and Its Expression in Escherichia coli

2012 ◽  
Vol 78 (15) ◽  
pp. 5238-5246 ◽  
Author(s):  
Dongfei Han ◽  
Ji-Young Ryu ◽  
Robert A. Kanaly ◽  
Hor-Gil Hur
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Putida ◽  
Hypothetical Protein ◽  
Aldehyde Group ◽  
Agrobacterium Vitis ◽  
T7 Promoter ◽  
Content Type ◽  
E Coli ◽  
Cell Extracts ◽  
Isoeugenol Monooxygenase

ABSTRACTA plasmid, pTA163, inEscherichia colicontained an approximately 34-kb gene fragment fromPseudomonas putidaJYR-1 that included the genes responsible for the metabolism oftrans-anethole to protocatechuic acid. Three Tn5-disrupted open reading frame 10 (ORF 10) mutants of plasmid pTA163 lost their abilities to catalyzetrans-anethole. Heterologously expressed ORF 10 (1,047 nucleotides [nt]) under a T7 promoter inE. colicatalyzed oxidative cleavage of a propenyl group oftrans-anethole to an aldehyde group, resulting in the production ofpara-anisaldehyde, and this gene was designatedtao(trans-anetholeoxygenase). The deduced amino acid sequence of TAO had the highest identity (34%) to a hypothetical protein ofAgrobacterium vitisS4 and likely contained a flavin-binding site. Preferred incorporation of an oxygen molecule from water intop-anisaldehyde using18O-labeling experiments indicated stereo preference of TAO for hydrolysis of the epoxide group. Interestingly, unlike the narrow substrate range of isoeugenol monooxygenase fromPseudomonas putidaIE27 andPseudomonas nitroreducensJin1, TAO fromP. putidaJYR-1 catalyzed isoeugenol,O-methyl isoeugenol, and isosafrole, all of which contain the 2-propenyl functional group on the aromatic ring structure. Addition of NAD(P)H to the ultrafiltered cell extracts ofE. coli(pTA163) increased the activity of TAO. Due to the relaxed substrate range of TAO, it may be utilized for the production of various fragrance compounds from plant phenylpropanoids in the future.

scholarly journals Cytochromes c Constitute a Layer of Protection against Nitric Oxide but Not Nitrite

2018 ◽  
Vol 84 (17) ◽  
Author(s):  
Qiu Meng ◽  
Yijuan Sun ◽  
Haichun Gao
Keyword(s):  
Nitric Oxide ◽  
Specific Activity ◽  
Shewanella Oneidensis ◽  
Main Role ◽  
Content Type ◽  
Environmental Bacterium ◽  
Enzymatic Systems ◽  
Bacteriostatic Agent ◽  
Protective Proteins

ABSTRACT Nitric oxide (NO) is a radical gas that reacts with various biological molecules in complex ways to inhibit growth as a bacteriostatic agent. NO is nearly ubiquitous because it can be generated both biotically and abiotically. To protect the cell from NO damage, bacteria have evolved many strategies, with the production of detoxifying enzymatic systems being the most efficient. Here, we report that c-type cytochromes (cytochromes c) constitute a primary NO protection system in Shewanella oneidensis, a Gram-negative environmental bacterium renowned for respiratory versatility due to its high cytochrome c content. By using mutants producing cytochromes c at varying levels, we found that the content of these proteins is inversely correlated with the growth inhibition imposed by NO, whereas the effect of each individual cytochrome c is negligible. This NO-protecting system has no effect on nitrite inhibition. In the absence of cytochromes c, other NO targets and protective proteins, such as NnrS, emerge to show physiological influences during the NO stress. We further demonstrate that cytochromes c also play a similar role in Escherichia coli, albeit only modestly. Our data thus identify the in vivo function of an important group of proteins in alleviating NO stress. IMPORTANCE It is widely accepted that the antibacterial effects of nitrite are attributable to nitric oxide (NO) formation, suggesting a correlation of bacterial susceptibilities to these two chemicals. However, compared to E. coli, S. oneidensis is highly sensitive to nitrite but resistant to NO, implying the presence of robust NO-protective systems. Here, we show that c-type cytochromes (cytochromes c) play a main role in protecting S. oneidensis against damages from NO but not from nitrite. In their absence, impacts of proteins that promote NO tolerance and that are targets of NO inhibition become evident. Our data thus reveal the specific activity of cytochromes c in alleviating the stress caused by NO but not nitrite.

scholarly journals A Toxic Environment: a Growing Understanding of How Microbial Communities Affect Escherichia coli O157:H7 Shiga Toxin Expression

2020 ◽  
Vol 86 (24) ◽  
Author(s):  
Erin M. Nawrocki ◽  
Hillary M. Mosso ◽  
Edward G. Dudley
Keyword(s):  
Escherichia Coli ◽  
Shiga Toxin ◽  
Microbial Interactions ◽  
Severe Illness ◽  
Content Type ◽  
E Coli ◽  
Wide Range ◽  
Lambdoid Prophage

ABSTRACT Enterohemorrhagic Escherichia coli (EHEC) strains, including E. coli O157:H7, cause severe illness in humans due to the production of Shiga toxin (Stx) and other virulence factors. Because Stx is coregulated with lambdoid prophage induction, its expression is especially susceptible to environmental cues. Infections with Stx-producing E. coli can be difficult to model due to the wide range of disease outcomes: some infections are relatively mild, while others have serious complications. Probiotic organisms, members of the gut microbiome, and organic acids can depress Stx production, in many cases by inhibiting the growth of EHEC strains. On the other hand, the factors currently known to amplify Stx act via their effect on the stx-converting phage. Here, we characterize two interactive mechanisms that increase Stx production by O157:H7 strains: first, direct interactions with phage-susceptible E. coli, and second, indirect amplification by secreted factors. Infection of susceptible strains by the stx-converting phage can expand the Stx-producing population in a human or animal host, and phage infection has been shown to modulate virulence in vitro and in vivo. Acellular factors, particularly colicins and microcins, can kill O157:H7 cells but may also trigger Stx expression in the process. Colicins, microcins, and other bacteriocins have diverse cellular targets, and many such molecules remain uncharacterized. The identification of additional Stx-amplifying microbial interactions will improve our understanding of E. coli O157:H7 infections and help elucidate the intricate regulation of pathogenicity in EHEC strains.

scholarly journals In Vivo Bioluminescent Monitoring of Therapeutic Efficacy and Pharmacodynamic Target Assessment of Antofloxacin against Escherichia coli in a Neutropenic Murine Thigh Infection Model

2017 ◽  
Vol 62 (1) ◽  
Author(s):  
Yu-Feng Zhou ◽  
Meng-Ting Tao ◽  
Yu-Zhang He ◽  
Jian Sun ◽  
Ya-Hong Liu ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Subcutaneous Administration ◽  
Free Drug ◽  
Infection Model ◽  
Bioluminescent Imaging ◽  
Time Curve ◽  
Content Type ◽  
E Coli ◽  
Tract Infections

ABSTRACT Antimicrobial resistance among uropathogens has increased the rates of infection-related morbidity and mortality. Antofloxacin is a novel fluoroquinolone with broad-spectrum antibacterial activity against urinary Gram-negative bacilli, such as Escherichia coli. This study monitored the in vivo efficacy of antofloxacin using bioluminescent imaging and determined pharmacokinetic (PK)/pharmacodynamic (PD) targets against E. coli isolates in a neutropenic murine thigh infection model. The PK properties were determined after subcutaneous administration of antofloxacin at 2.5, 10, 40, and 160 mg/kg of body weight. Following thigh infection, the mice were treated with 2-fold-increasing doses of antofloxacin from 2.5 to 80 mg/kg administered every 12 h. Efficacy was assessed by quantitative determination of the bacterial burdens in thigh homogenates and was compared with the bioluminescent density. Antofloxacin demonstrated both static and killing endpoints in relation to the initial burden against all study strains. The PK/PD index area under the concentration-time curve (AUC)/MIC correlated well with efficacy (R 2 = 0.92), and the dose-response relationship was relatively steep, as observed with escalating doses of antofloxacin. The mean free drug AUC/MIC targets necessary to produce net bacterial stasis and 1-log10 and 2-log10 kill for each isolate were 38.7, 66.1, and 147.0 h, respectively. In vivo bioluminescent imaging showed a rapid decrease in the bioluminescent density at free drug AUC/MIC exposures that exceeded the stasis targets. The integration of these PD targets combined with the results of PK studies with humans will be useful in setting optimal dosing regimens for the treatment of urinary tract infections due to E. coli.

scholarly journals In Vivo mRNA Profiling of Uropathogenic Escherichia coli from Diverse Phylogroups Reveals Common and Group-Specific Gene Expression Profiles

mBio ◽  
2014 ◽  
Vol 5 (4) ◽  
Author(s):  
Piotr Bielecki ◽  
Uthayakumar Muthukumarasamy ◽  
Denitsa Eckweiler ◽  
Agata Bielecka ◽  
Sarah Pohl ◽  
...  
Keyword(s):  
Gene Expression ◽  
Escherichia Coli ◽  
Expression Profiles ◽  
Gene Expression Profiles ◽  
Specific Gene ◽  
Content Type ◽  
E Coli ◽  
Human Host ◽  
Tract Infections

ABSTRACTmRNA profiling of pathogens during the course of human infections gives detailed information on the expression levels of relevant genes that drive pathogenicity and adaptation and at the same time allows for the delineation of phylogenetic relatedness of pathogens that cause specific diseases. In this study, we used mRNA sequencing to acquire information on the expression ofEscherichia colipathogenicity genes during urinary tract infections (UTI) in humans and to assign the UTI-associatedE. coliisolates to different phylogenetic groups. Whereas thein vivogene expression profiles of the majority of genes were conserved among 21E. colistrains in the urine of elderly patients suffering from an acute UTI, the specific gene expression profiles of the flexible genomes was diverse and reflected phylogenetic relationships. Furthermore, genes transcribedin vivorelative to laboratory media included well-described virulence factors, small regulatory RNAs, as well as genes not previously linked to bacterial virulence. Knowledge on relevant transcriptional responses that drive pathogenicity and adaptation of isolates to the human host might lead to the introduction of a virulence typing strategy into clinical microbiology, potentially facilitating management and prevention of the disease.IMPORTANCEUrinary tract infections (UTI) are very common; at least half of all women experience UTI, most of which are caused by pathogenicEscherichia colistrains. In this study, we applied massive parallel cDNA sequencing (RNA-seq) to provide unbiased, deep, and accurate insight into the nature and the dimension of the uropathogenicE. coligene expression profile during an acute UTI within the human host. This work was undertaken to identify key players in physiological adaptation processes and, hence, potential targets for new infection prevention and therapy interventions specifically aimed at sabotaging bacterial adaptation to the human host.

scholarly journals Role of Urinary Cathelicidin LL-37 and Human β-Defensin 1 in Uncomplicated Escherichia coli Urinary Tract Infections

2014 ◽  
Vol 82 (4) ◽  
pp. 1572-1578 ◽  
Author(s):  
Karen L. Nielsen ◽  
Pia Dynesen ◽  
Preben Larsen ◽  
Lotte Jakobsen ◽  
Paal S. Andersen ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Urinary Tract ◽  
Urinary Tract Infections ◽  
Adult Women ◽  
Content Type ◽  
E Coli ◽  
Innate Defense ◽  
High Level ◽  
Tract Infections

ABSTRACTCathelicidin (LL-37) and human β-defensin 1 (hBD-1) are important components of the innate defense in the urinary tract. The aim of this study was to characterize whether these peptides are important for developing uncomplicatedEscherichia coliurinary tract infections (UTIs). This was investigated by comparing urinary peptide levels of UTI patients during and after infection to those of controls, as well as characterizing the fecal flora of participants with respect to susceptibility to LL-37 andin vivovirulence. Forty-seven UTI patients and 50 controls who had never had a UTI were included. Participants were otherwise healthy, premenopausal, adult women. LL-37 MIC levels were compared for fecalE. coliclones from patients and controls and were also compared based on phylotypes (A, B1, B2, and D).In vivovirulence was investigated in the murine UTI model by use of selected fecal isolates from patients and controls. On average, UTI patients had significantly more LL-37 in urine during infection than postinfection, and patient LL-37 levels postinfection were significantly lower than those of controls. hBD-1 showed similar urine levels for UTI patients and controls. FecalE. coliisolates from controls had higher LL-37 susceptibility than fecal and UTIE. coliisolates from UTI patients.In vivostudies showed a high level of virulence of fecalE. coliisolates from both patients and controls and showed no difference in virulence correlated with the LL-37 MIC level. The results indicate that the concentration of LL-37 in the urinary tract and low susceptibility to LL-37 may increase the likelihood of UTI in a complex interplay between host and pathogen attributes.

scholarly journals Magnesium Sensing Regulates Intestinal Colonization of Enterohemorrhagic Escherichia coli O157:H7

mBio ◽  
2020 ◽  
Vol 11 (6) ◽  
Author(s):  
Yutao Liu ◽  
Runhua Han ◽  
Junyue Wang ◽  
Pan Yang ◽  
Fang Wang ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Large Intestine ◽  
Intestinal Tract ◽  
Regulatory System ◽  
Regulatory Pathway ◽  
Content Type ◽  
E Coli ◽  
Low Magnesium ◽  
Enterocyte Effacement

ABSTRACT The large intestinal pathogen enterohemorrhagic Escherichia coli (EHEC) O157:H7 detects host cues to regulate virulence gene expression during colonization and infection. However, virulence regulatory mechanisms of EHEC O157:H7 in the human large intestine are not fully understood. Herein, we identified a virulence-regulating pathway where the PhoQ/PhoP two-component regulatory system senses low magnesium levels and signals to the O island 119-encoded Z4267 (LmiA; low magnesium-induced regulator A), directly activating loci of enterocyte effacement genes to promote EHEC O157:H7 adherence in the large intestine. Disruption of this pathway significantly decreased EHEC O157:H7 adherence in the mouse intestinal tract. Moreover, feeding mice a magnesium-rich diet significantly reduced EHEC O157:H7 adherence in vivo. This LmiA-mediated virulence regulatory pathway is also conserved among several EHEC and enteropathogenic E. coli serotypes; therefore, our findings support the use of magnesium as a dietary supplement and provide greater insights into the dietary cues that can prevent enteric infections. IMPORTANCE Sensing specific gut metabolites is an important strategy for inducing crucial virulence programs by enterohemorrhagic Escherichia coli (EHEC) O157:H7 during colonization and infection. Here, we identified a virulence-regulating pathway wherein the PhoQ/PhoP two-component regulatory system signals to the O island 119-encoded low magnesium-induced regulator A (LmiA), which, in turn, activates locus of enterocyte effacement (LEE) genes to promote EHEC O157:H7 adherence in the low-magnesium conditions of the large intestine. This regulatory pathway is widely present in a range of EHEC and enteropathogenic E. coli (EPEC) serotypes. Disruption of this pathway significantly decreased EHEC O157:H7 adherence in the mouse intestinal tract. Moreover, mice fed a magnesium-rich diet showed significantly reduced EHEC O157:H7 adherence in vivo, indicating that magnesium may help in preventing EHEC and EPEC infection in humans.

scholarly journals Role of F1C Fimbriae, Flagella, and Secreted Bacterial Components in the Inhibitory Effect of Probiotic Escherichia coli Nissle 1917 on Atypical Enteropathogenic E. coli Infection

2014 ◽  
Vol 82 (5) ◽  
pp. 1801-1812 ◽  
Author(s):  
Sylvia Kleta ◽  
Marcel Nordhoff ◽  
Karsten Tedin ◽  
Lothar H. Wieler ◽  
Rafal Kolenda ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Molecular Mechanisms ◽  
Inhibitory Effect ◽  
Host Cells ◽  
Single Infection ◽  
Content Type ◽  
E Coli ◽  
Initial Adhesion

ABSTRACTEnteropathogenicEscherichia coli(EPEC) is recognized as an important intestinal pathogen that frequently causes acute and persistent diarrhea in humans and animals. The use of probiotic bacteria to prevent diarrhea is gaining increasing interest. The probioticE. colistrain Nissle 1917 (EcN) is known to be effective in the treatment of several gastrointestinal disorders. While bothin vitroandin vivostudies have described strong inhibitory effects of EcN on enteropathogenic bacteria, including pathogenicE. coli, the underlying molecular mechanisms remain largely unknown. In this study, we examined the inhibitory effect of EcN on infections of porcine intestinal epithelial cells with atypical enteropathogenicE. coli(aEPEC) with respect to single infection steps, including adhesion, microcolony formation, and the attaching and effacing phenotype. We show that EcN drastically reduced the infection efficiencies of aEPEC by inhibiting bacterial adhesion and growth of microcolonies, but not the attaching and effacing of adherent bacteria. The inhibitory effect correlated with EcN adhesion capacities and was predominantly mediated by F1C fimbriae, but also by H1 flagella, which served as bridges between EcN cells. Furthermore, EcN seemed to interfere with the initial adhesion of aEPEC to host cells by secretion of inhibitory components. These components do not appear to be specific to EcN, but we propose that the strong adhesion capacities enable EcN to secrete sufficient local concentrations of the inhibitory factors. The results of this study are consistent with a mode of action whereby EcN inhibits secretion of virulence-associated proteins of EPEC, but not their expression.

scholarly journals The Topology of the l-Arginine Exporter ArgO Conforms to an Nin-CoutConfiguration in Escherichia coli: Requirement for the Cytoplasmic N-Terminal Domain, Functional Helical Interactions, and an Aspartate Pair for ArgO Function

2016 ◽  
Vol 198 (23) ◽  
pp. 3186-3199 ◽  
Author(s):  
Amit Pathania ◽  
Arvind Kumar Gupta ◽  
Swati Dubey ◽  
Balasubramanian Gopal ◽  
Abhijit A. Sardesai
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Cytoplasmic Membrane ◽  
Basic Amino Acid ◽  
Intramolecular Interactions ◽  
Membrane Topology ◽  
Content Type ◽  
E Coli ◽  
Terminal Domain

ABSTRACTArgO and LysE are members of the LysE family of exporter proteins and ordinarily mediate the export ofl-arginine (Arg) inEscherichia coliandl-lysine (Lys) and Arg inCorynebacterium glutamicum, respectively. Under certain conditions, ArgO also mediates Lys export. To delineate the arrangement of ArgO in the cytoplasmic membrane ofE. coli, we have employed a combination of cysteine accessibilityin situ, alkaline phosphatase fusion reporters, and protein modeling to arrive at a topological model of ArgO. Our studies indicate that ArgO assumes an Nin-Coutconfiguration, potentially forming a five-transmembrane helix bundle flanked by a cytoplasmic N-terminal domain (NTD) comprising roughly its first 38 to 43 amino acyl residues and a short periplasmic C-terminal region (CTR). Mutagenesis studies indicate that the CTR, but not the NTD, is dispensable for ArgO functionin vivoand that a pair of conserved aspartate residues, located near the opposing edges of the cytoplasmic membrane, may play a pivotal role in facilitating transmembrane Arg flux. Additional studies on amino acid substitutions that impair ArgO functionin vivoand their derivatives bearing compensatory amino acid alterations indicate a role for intramolecular interactions in the Arg export mechanism, and some interactions are corroborated by normal-mode analyses. Lastly, our studies suggest that ArgO may exist as a monomerin vivo, thus highlighting the requirement for intramolecular interactions in ArgO, as opposed to interactions across multiple ArgO monomers, in the formation of an Arg-translocating conduit.IMPORTANCEThe orthologous proteins LysE ofC. glutamicumand ArgO ofE. colifunction as exporters of the basic amino acidsl-arginine andl-lysine and the basic amino acidl-arginine, respectively, and LysE can functionally substitute for ArgO when expressed inE. coli. Notwithstanding this functional equivalence, studies reported here show that ArgO possesses a membrane topology that is distinct from that reported for LysE, with substantial variation in the topological arrangement of the proximal one-third portions of the two exporters. Additional genetic andin silicostudies reveal the importance of (i) the cytoplasmic N-terminal domain, (ii) a pair of conserved aspartate residues, and (iii) potential intramolecular interactions in ArgO function and indicate that an Arg-translocating conduit is formed by a monomer of ArgO.

scholarly journals Shape Changes and Interaction Mechanism of Escherichia coli Cells Treated with Sericin and Use of a Sericin-Based Hydrogel for Wound Healing

2016 ◽  
Vol 82 (15) ◽  
pp. 4663-4672 ◽  
Author(s):  
Rui Xue ◽  
Yalong Liu ◽  
Qingsong Zhang ◽  
Congcong Liang ◽  
Huazhen Qin ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Escherichia Coli ◽  
Cell Membrane ◽  
Interaction Mechanism ◽  
Bacterial Cells ◽  
Content Type ◽  
E Coli ◽  
Membrane Blebbing ◽  
Sterile Gauze

ABSTRACTTo verify the interaction mechanism between sericin andEscherichia coli, especially the morphological and structural changes in the bacterial cells, the antimicrobial activity of sericin againstE. colias a model for Gram-negative bacteria was investigated. The antibacterial activity of sericin onE. coliand the interaction mechanism were investigated in this study by analyzing the growth, integrity, and morphology of the bacterial cells following treatment with sericin. The changes in morphology and cellular compositions of bacterial cells treated with sericin were observed by an inverted fluorescence microscope, scanning electron microscopy, and transmission electron microscopy. Changes in electrical conductivity, total sugar concentration of the broth for the bacteria, and protein expression of the bacteria were determined to investigate the permeability of the cell membrane. A sericin-based hydrogel was prepared for anin vivostudy of wound dressing. The results showed that the antibacterial activity of the hydrogel increased with the increase in the concentration of sericin from 10 g/liter to 40 g/liter. The introduction of sericin induces membrane blebbing ofE. colicells caused by antibiotic action on the cell membrane. The cytoplasm shrinkage phenomenon was accompanied by blurring of the membrane wall boundaries. WhenE. colicells were treated with sericin, release of intracellular components quickly increased. The electrical conductivity assay indicated that the charged ions are reduced after exposure to sericin so that the integrity of the cell membrane is weakened and metabolism is blocked. In addition, sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that sericin hinders the expression of bacterial protein. Sericin may damage the integrity of the bacterial cell membrane, thereby eventually inhibiting the growth and reproduction ofE. coli. Compared to sterile gauze, the sericin-based hydrogel promoted fibroblast cell proliferation and accelerated the formation of granulation tissues and neovessels.IMPORTANCEThe specific relationship and interaction mechanism between sericin andE. colicells were investigated and elucidated. The results show that after 12 h of treatment, sericin molecules induce membrane blebbing ofE. colicells, and the bacteria show decreases in liquidity and permeability of biological membrane, resulting in alterations in the conductivity of the culture medium and the integrity of the outer membrane. The subsequentin vivoresults demonstrate that the sericin-poly(N-isopropylacrylamide-N,N′-methylene-bis-acrylamide [NIPAm-MBA]) hydrogel accelerated wound healing compared to that with sterile gauze, which is a beneficial result for future applications in clinical medicine and the textile, food, and coating industries.

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