Bryan Andrew, Roesch Paula, Davis Lindsay, Moritz Rebecca, Pellett Shahaireen, Welch Rodney A
Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706, USA.
Infect Immun. 2006 Feb;74(2):1072-83. doi: 10.1128/IAI.74.2.1072-1083.2006.
Genomic DNA sequence analysis of the uropathogenic Escherichia coli strain CFT073 revealed that besides the fimB and fimE recombinase genes that control the type 1 pilus fim phase switch, there are three additional fimB- and fimE-like genes: ipuA, ipuB, and ipbA. Alignment of the predicted amino acid sequences showed that the five recombinases range in sequence similarity from 63 to 70%. An epidemiological survey indicates that ipuA and ipuB are present and linked next to the dsdCXA locus in 24 of 67 uropathogenic E. coli strains but are found in only 1 of 15 normal human fecal isolates. The ipbA sequence located next to the betABIT locus was found in 42 of 67 uropathogenic isolates and 8 of 15 of the commensal strains. We show that two of these recombinases, those encoded by ipuA and ipbA, can function at the type 1 pilus fim switch. In a CFT073 deletion mutant lacking all five recombinase genes, recombinant ipuA or ipbA provided in trans inverted the fim element from the off state to the on state. When a fim OFF CFT073 DeltafimBE mutant was used to infect the urinary tracts of mice, a switch to the fim on state was detected within 24 h in bacteria recovered from urine, the bladder, and the kidneys. A fim OFF CFT073 DeltafimBE ipuB ipbA mutant also demonstrated the ability to switch from the fim off state to the on state during mouse infection. CFT073 recombinase mutants derived from isolates in either the fim on or off state showed a reciprocal relationship for motility. Switches from a nonmotile to a motile phenotype and from a fim on to off genotype were observed in fim ON CFT073 DeltafimBE ipuAB ipbA mutants when ipuA or fimB was provided in trans. Together these results indicate that ipuA has fimB-like on-to-off and off-to-on fim switching activity and that ipbA has the ability to switch fim from the off to the on orientation.
对尿路致病性大肠杆菌菌株CFT073的基因组DNA序列分析显示，除了控制1型菌毛fim相开关的fimB和fimE重组酶基因外，还有另外三个类fimB和类fimE基因：ipuA、ipuB和ipbA。预测氨基酸序列的比对表明，这五种重组酶的序列相似性在63%至70%之间。一项流行病学调查表明，在67株尿路致病性大肠杆菌菌株中的24株中，ipuA和ipuB存在且与dsdCXA基因座相邻，但在15株正常人粪便分离株中仅在1株中发现。在67株尿路致病性分离株中的42株以及15株共生菌株中的8株中发现了位于betABIT基因座旁边的ipbA序列。我们发现，这些重组酶中的两种，即由ipuA和ipbA编码的重组酶，可在1型菌毛fim开关处发挥作用。在一个缺失所有五种重组酶基因的CFT073缺失突变体中，反式提供的重组ipuA或ipbA将fim元件从关闭状态转换为开启状态。当使用fim OFF CFT073 ΔfimBE突变体感染小鼠尿路时，在从尿液、膀胱和肾脏中回收的细菌中，24小时内检测到向fim开启状态的转换。fim OFF CFT073 ΔfimBE ipuB ipbA突变体在小鼠感染期间也表现出从fim关闭状态转换为开启状态的能力。源自fim开启或关闭状态分离株的CFT073重组酶突变体在运动性方面呈现出相反的关系。当反式提供ipuA或fimB时，在fim ON CFT073 ΔfimBE ipuAB ipbA突变体中观察到从非运动表型到运动表型以及从fim开启基因型到关闭基因型的转换。这些结果共同表明，ipuA具有类似fimB的开启到关闭和关闭到开启的fim转换活性，并且ipbA具有将fim从关闭方向转换为开启方向的能力。
