Abstract

Serratia marcescens NJ01, a Gram-negative bacterium, can infect tomato leaves and cause chlorosis and wilting. The present study evaluated the quorum sensing (QS) and biofilm inhibitory effects of seven carboline compounds against S. marcescens NJ01 at 20 μg ml⁻¹, and subsequently focused the study on norharmane as this had the best inhibitory activity. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis confirmed the down-regulation of QS and biofilm related genes bsmA, bsmB, fimA, fimC, flhD, pigA, pigC and shlA on exposure to norharmane. Fourier-Transform Infrared Spectroscopy (FT-IR) analysis showed a reduction in the major components of the exopolysaccharide (EPS) matrix such as nucleic acids, proteins and fatty acids, which are involved in forming the tertiary structure of biofilms. Norharmane exposure also enhanced the susceptibility of the biofilm to ofloxacin. Hence, norharmane has the potential for use as an antibiotic adjuvant to enhance the efficacy of conventional antibiotics to reduce pathogenic bacterial infections.

摘要

粘质沙雷氏菌NJ01是一种革兰氏阴性细菌，可感染番茄叶片并引起萎黄和枯萎。本研究评估了20μgml ^-1时7种碳氢化合物对粘质沙门氏菌NJ01的群体感应（QS）和生物膜抑制作用，随后将研究集中于正畸烷，因为这具有最佳的抑制活性。实时定量聚合酶链反应（qRT-PCR）分析证实了QS和生物膜相关基因bsmA，bsmB，fimA，fimC，flhD，pigA，pigC和shlA的下调暴露于正己烷中。傅里叶变换红外光谱（FT-IR）分析表明，胞外多糖（EPS）基质的主要成分（如核酸，蛋白质和脂肪酸）减少，这些成分参与形成生物膜的三级结构。去氯烷的暴露也增强了生物膜对氧氟沙星的敏感性。因此，降氯烷具有用作抗生素佐剂的潜力，以增强常规抗生素减少病原性细菌感染的功效。