Antimicrobial effects and membrane damage mechanism of blueberry(Vaccinium corymbosum L.) extract against Vibrio parahaemolyticus

Authors: SUN, XIAOHONG - Shanghai Ocean University; HAO, LI-RAN - Shanghai Ocean University; XIE, QING-CHAO - Shanghai Ocean University; LAN, WEI-QING - Shanghai Ocean University; ZHAO, YONG - Shanghai Ocean University; PAN, YING-JIE - Shanghai Ocean University; Wu, Vivian

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2019
Publication Date: 11/26/2019
Citation: Sun, X., Hao, L., Xie, Q., Lan, W., Zhao, Y., Pan, Y., Wu, V.C. 2019. Antimicrobial effects and membrane damage mechanism of blueberry (Vaccinium corymbosum L.) extract against Vibrio parahaemolyticus. Food Control. 111:107020. https://doi.org/10.1016/j.foodcont.2019.107020.
DOI: https://doi.org/10.1016/j.foodcont.2019.107020

Interpretive Summary: Vibrio parahaemolyticus is a Gram-negative bacterium that generally attaches or invades zooplankton, fish, shellfish, and other aquatic products. It is a marine pathogen that causes diseases in aquatic products, resulting in severe economic losses for the aquaculture industry. V. parahaemolyticus is also frequently implicated in foodborne illnesses related to consumption of raw or undercooked seafood. The most common treatment for bacterial diseases is antibiotic therapy, but the emergence of antibiotic-resistant bacteria is a major problem worldwide. The high level of antibiotic resistance is a serious threat to global health. This present study the antimicrobial effect and membrane damage mechanism of blueberry extract against Vibrio parahaemolyticus. The results indicated that blueberry extract had strong antimicrobial effect against three V. parahaemolyticus strains. Blueberry extract disrupted cell membrane integrity, interrupted normal growth of bacterial cells, and obviously altered the expression of seven membrane genes, compared to that in the controls. These findings suggested that blueberry extract inhibited the growth of V. parahaemolyticus at the molecular level rather than via physical damage. The information provided in this study is important because it shows blueberry extract as a natural alternative antibacterial agent to control pathogenic bacteria. Thus, blueberry extract has high potential for future development as a natural and green preservative.

Technical Abstract: This study aimed to investigate the antimicrobial effect and membrane damage mechanism of blueberry extract against Vibrio parahaemolyticus. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of blueberry extract against three strains of V. parahaemolyticus (ATCC 33847, ATCC 17802, and F 13) were firstly determined. The effect of blueberry extract on V. parahaemolyticus cell membrane was further visualized by scanning electron microscopy and transmission electron microscopy. We examined the antimicrobial mechanism of blueberry extract in regulation of the expression of seven membrane genes. The MIC for V. parahaemolyticus ATCC 17802, ATCC 33847, and F 13 was 25, 25, and 12.5 mg/mL, respectively, whereas the MBC was 50, 50, and 25 mg/mL, respectively. The V. parahaemolyticus exposed to 1× MIC showed distorted membrane morphology and leakage of cellular contents. The cytoplasmic constituents were aggregated, causing a wide range of hollow areas in the cells. The expression of two outer membrane protein genes (tolC and fla) and five inner membrane protein genes [transcription termination factor (nusA), long-chain fatty acid transport protein gene (fadL), elongation factor Tu (ef-Tu), ATP synthase F1 alpha subunit (atpA), and dihydrolipoamide dehydrogenase gene (dld)] in V. parahaemolyticus treated with or without blueberry extract was investigated by quantitative real-time PCR. Compared to that in the control, the gene expression of fadL and nusA was upregulated by 1.1-, 2.1-, 4.1-fold and 7.4-, 4.3-, 3.6-fold in V. parahaemolyticus ATCC 17802, ATCC 33847, and F 13, respectively. The gene expression of ef-Tu was downregulated by 1.1-, 2.7-, 3.3-fold in the three strains of V. parahaemolyticus. Findings from this study revealed that blueberry extract had strong antibacterial effect and inhibited gene transcription to disrupt cell membrane structure and energy transport. Further studies investigating potential antimicrobial applications of blueberry extract are necessary to provide a basis for the development and utilization of blueberries as an antimicrobial agent.