Monday S R, Schiller N L
Division of Biomedical Sciences, University of California, Riverside 92521-0121, USA.
J Bacteriol. 1996 Feb;178(3):625-32. doi: 10.1128/jb.178.3.625-632.1996.
Previous studies localized an alginate lyase gene (algL) within the alginate biosynthetic gene cluster at 34 min on the Pseudomonas aeruginosa chromosome. Insertion of a Tn501 polar transposon in a gene (algX) directly upstream of algL in mucoid P. aeruginosa FRD1 inactivated expression of algX, algL, and other downstream genes, including algA. This strain is phenotypically nonmucoid; however, alginate production could be restored by complementation in trans with a plasmid carrying all of the genes inactivated by the insertion, including algL and algX. Alginate production was also recovered when a merodiploid that generated a complete alginate gene cluster on the chromosome was constructed. However, alginate production by merodiploids formed in the algX::Tn501 mutant using an alginate cluster with an algL deletion was not restored to wild-type levels unless algL was provided on a plasmid in trans. In addition, complementation studies of Tn501 mutants using plasmids containing specific deletions in either algL or algX revealed that both genes were required to restore the mucoid phenotype. Escherichia coli strains which expressed algX produced a unique protein of approximately 53 kDa, consistent with the gene product predicted from the DNA sequencing data. These studies demonstrate that AlgX, whose biochemical function remains to be defined, and AlgL, which has alginate lyase activity, are both involved in alginate production by P. aeruginosa.
先前的研究将一个藻酸盐裂解酶基因（algL）定位在铜绿假单胞菌染色体上34分钟处的藻酸盐生物合成基因簇内。在黏液型铜绿假单胞菌FRD1中，在algL正上游的一个基因（algX）中插入一个Tn501极性转座子，使algX、algL和其他下游基因（包括algA）的表达失活。该菌株在表型上是非黏液型的；然而，通过用携带因插入而失活的所有基因（包括algL和algX）的质粒进行反式互补，可以恢复藻酸盐的产生。当构建一个在染色体上产生完整藻酸盐基因簇的部分二倍体时，藻酸盐的产生也得以恢复。然而，在algX::Tn501突变体中使用缺失algL的藻酸盐基因簇形成的部分二倍体产生的藻酸盐，除非在反式中通过质粒提供algL，否则不会恢复到野生型水平。此外，使用在algL或algX中含有特定缺失的质粒对Tn501突变体进行的互补研究表明，这两个基因都是恢复黏液型表型所必需的。表达algX的大肠杆菌菌株产生了一种约53 kDa的独特蛋白质，这与DNA测序数据预测的基因产物一致。这些研究表明，其生化功能尚待确定的AlgX和具有藻酸盐裂解酶活性的AlgL都参与了铜绿假单胞菌的藻酸盐产生。
