Powder coating of nonconductors

Abstract

Azotobacter vinelandii is a γ-proteobacterium belonging to the Pseudomonadaceae family, that is capable of developing a differentiation process leading to the formation of cysts resistant to desiccation. The morphological, metabolic and biochemical changes occurring during encystment have been extensively studied. To elucidate the molecular basis of this process, the proteome of cells undergoing encystment was determined by quantitative proteomic analysis by LC-MS/MS. We identified 312 proteins differentially expressed after 48 h of encystment induction, with respect to vegetative cells. In agreement with the biochemical and physiological changes known to occur during this process, we found modifications in the abundance of proteins involved in nitrogen fixation, synthesis of the flagella, cell division, the glyoxilate shunt and in the synthesis of phenolic lipids known to replace the membrane phospholipids during cyst formation. In addition, our analysis also identified proteins for other cellular processes, probably important for desiccation resistance, such as the synthesis of trehalose. Proteins previously identified as critical for cyst development, also exhibited differences in abundance during encystment induction. This work represents the first study of the global changes in protein abundance during cysts development, and contributes to a better understanding of the molecular mechanism underlying this differentiation process.Azotobacter vinelandii has been an important model for the study of the cyst developmental process in Gram-negative bacteria. In the current study, we have used a large-scale proteomic approach, using quantitative proteomic analysis by LC-MS/MS, to document changes in protein abundance in A. vinelandii cysts, relative to vegetative growing conditions. A total of 312 proteins were identified with differences in their abundance after 48 h of encystment induction. Remarkably, 62 proteins were found exclusively in the differentiated cell. As expected, some of the identified proteins were related to processes previously reported to occur during cyst development. However, the predicted functional categorization also revealed other biological processes likely important for the successful formation of the cyst. We believe that these novel findings not only help us to better understand the molecular basis of the developmental life cycle of A. vinelandii, but also the global molecular changes occurring during cyst formation in other Gram-negative bacteria.