Genetic analysis of bacterial functions involved in biofilm formation

1.细菌生物膜(Bf)的耐药性被认为是由于胞外多糖(EPS)阻碍药物扩散所致。在寻找其他耐药原因的过程中，我们分离到了粘质沙雷氏菌突变株，它们能够构建厚的Bf，但形成的Bf在产生耐药性方面存在缺陷。由于这些突变体的浮游细胞表现出正常的药物敏感性，这些突变体似乎在Bf特异性耐药机制上存在缺陷。3个已鉴定基因的测序和同源性分析表明，与内毒素和EPS的生物合成相关的功能以及铁载体的摄取可能与Bf2群体水平的耐药性有关。在Bf中，局部微环境如pH、营养盐浓度或O2是异质性的。因此，构成Bf的细菌是异质性的。因此，如果一些细菌处于抗药性状态，就很难根除Bf。我们发现铜绿假单胞菌和其他一些细菌…更多的毛虫在缺磷条件下，细胞膜成分由富磷脂转变为富鸟脂脂。细菌细胞膜的这种剧烈变化可能会引起对化学物质和物理化学因素的敏感性变化。因此，对生长在低磷条件下的细菌进行了药敏试验。细菌对抗菌药物的耐药性没有明显增加，但富含鸟脂膜的细菌表现出较强的耐酸性。与Bf共存的浮游细菌显示出更高的耐药性。从Bf释放的未知物质似乎与耐药性的增加有关。在MF膜对面的小室中，用浮游细菌检测Bf对膜透性的影响，Mf膜的另一面携带Bf。浮游细菌肯定表现出了更强的抗药性。此外，在用微滤膜隔开的小室中，我们发现了细菌，这些细菌应该是含Bf的小室中的细菌。发现了一种新的细菌活性--“膜过滤器(孔径0.22 mm)通过活性”。较少

1. Drug resistance of bacterial biofims (Bf) has been considered to be due to extracellular polysaccharide (EPS) which may hinder diffusion of drugs. In searching for other reasons of drug resistance, we isolated Serratia marcescens mutants which are able to construct thick Bf, but the formed Bf are defective in developing drug resistane. Since planktonic cells of these mutants showed normal drug susceptibility, these mutants seemed to be defective in Bf specific resistance mechanisms. Sequencing and homology analyses with three identified genes indicated that functions related to biosynthesis of LPS and EPS, and siderophore uptake may be involved in drug resistance at the population level of Bf.2. In Bf, local micro-conditions such as pH, concentration of nutrients or O_2 are heterogeneous. Consequently, bacteria composing Bf are heterogenous. So, if some bacteria are in drug resistant status, it will be difficult to eradicate Bf. We found that Pseudomonas aeruginosa and some other ba … More cterial species change their cellular membrane from phospholipid-rich to ornithinelipid-rich composition under phosphorus-poor condition. Such drastic changes in bacterial membranes may induce susceptibility changes to chemicals and physicochemical factors. So, bacteria growing under phosphorus-poor condition was examined for susceptibility. There were no remarkable resistance increase to antibacterial drugs, but bacteria having ornithinelipid-rich membrane showed strong acid resistance.3. Planktonic bacteria coexisting with Bf demonstrated increased drug resistance. Unknown substances released from Bf seemed to contribute to the increased drug resistance. Effects of membrane permeable substances from Bf were examined with planktonic bacteria in the chamber facing the MF membrane which carried Bf of P. aeruginosa on the another face. The planktonic bacteria certainly showed increased drug resistance. In addition, in the chamber separated by MF membrane we found bacteria which should be contained in the chamber with Bf. A novel bacterial activity, "membrane filter (pore size, 0.22 mm) passing-through activity" was discovered. Less