Denef V J, Patrauchan M A, Florizone C, Park J, Tsoi T V, Verstraete W, Tiedje J M, Eltis L D
Center for Microbial Ecology, Michigan State University, East Lansing, 48824, USA.
J Bacteriol. 2005 Dec;187(23):7996-8005. doi: 10.1128/JB.187.23.7996-8005.2005.
Recent microarray experiments suggested that Burkholderia xenovorans LB400, a potent polychlorinated biphenyl (PCB)-degrading bacterium, utilizes up to three apparently redundant benzoate pathways and a C(1) metabolic pathway during biphenyl and benzoate metabolism. To better characterize the roles of these pathways, we performed quantitative proteome profiling of cells grown on succinate, benzoate, or biphenyl and harvested during either mid-logarithmic growth or the transition between the logarithmic and stationary growth phases. The Bph enzymes, catabolizing biphenyl, were approximately 16-fold more abundant in biphenyl- versus succinate-grown cells. Moreover, the upper and lower bph pathways were independently regulated. Expression of each benzoate pathway depended on growth substrate and phase. Proteins specifying catabolism via benzoate dihydroxylation and catechol ortho-cleavage (ben-cat pathway) were approximately an order of magnitude more abundant in benzoate- versus biphenyl-grown cells at the same growth phase. The chromosomal copy of the benzoyl-coenzyme A (CoA) (box(C)) pathway was also expressed during growth on biphenyl: Box(C) proteins were approximately twice as abundant as Ben and Cat proteins under these conditions. By contrast, proteins of the megaplasmid copy of the benzoyl-CoA (box(M)) pathway were only detected in transition-phase benzoate-grown cells. Other proteins detected at increased levels in benzoate- and biphenyl-grown cells included general stress response proteins potentially induced by reactive oxygen species formed during aerobic aromatic catabolism. Finally, C(1) metabolic enzymes were present in biphenyl-grown cells during transition phase. This study provides insights into the physiological roles and integration of apparently redundant catabolic pathways in large-genome bacteria and establishes a basis for investigating the PCB-degrading abilities of this strain.
近期的微阵列实验表明，食 xenovorans LB400 是一种高效的多氯联苯（PCB）降解细菌，在联苯和苯甲酸代谢过程中，它利用多达三条明显冗余的苯甲酸途径和一条 C(1) 代谢途径。为了更好地描述这些途径的作用，我们对在琥珀酸盐、苯甲酸盐或联苯上生长，并在对数中期生长或对数生长期与稳定期之间的过渡期收获的细胞进行了定量蛋白质组分析。分解联苯的 Bph 酶在联苯生长的细胞中比在琥珀酸盐生长的细胞中丰富约 16 倍。此外，上、下 bph 途径受到独立调控。每条苯甲酸途径的表达取决于生长底物和生长阶段。在相同生长阶段，通过苯甲酸二羟基化和邻苯二酚邻位裂解进行分解代谢（苯甲酸 - 邻苯二酚途径）的蛋白质在苯甲酸生长的细胞中比在联苯生长的细胞中丰富约一个数量级。在联苯生长期间，苯甲酰辅酶 A（CoA）（box(C)）途径的染色体拷贝也有表达：在这些条件下，Box(C) 蛋白的丰度约为 Ben 和 Cat 蛋白的两倍。相比之下，苯甲酰辅酶 A（box(M)）途径的大质粒拷贝的蛋白质仅在过渡期苯甲酸生长的细胞中检测到。在苯甲酸和联苯生长的细胞中检测到水平升高的其他蛋白质包括可能由需氧芳香族分解代谢过程中形成的活性氧诱导的一般应激反应蛋白。最后，在过渡期，联苯生长的细胞中存在 C(1) 代谢酶。这项研究深入了解了大基因组细菌中明显冗余的分解代谢途径的生理作用及其整合情况，并为研究该菌株的 PCB 降解能力奠定了基础。
