The extracellular proteome of Rhizobium etli CE3 in exponential and stationary growth phase

Abstract

BackgroundThe extracellular proteome or secretome of symbiotic bacteria like Rhizobium etli is presumed to be a key element of their infection strategy and survival. Rhizobia infect the roots of leguminous plants and establish a mutually beneficial symbiosis. To find out the possible role of secreted proteins we analyzed the extracellular proteome of R. etli CE3 in the exponential and stationary growth phases in minimal medium, supplemented with succinate-ammonium.ResultsThe extracellular proteins were obtained by phenol extraction and identified by LC-ESI MS/MS. We identified 192 and 191 proteins for the exponential and stationary phases respectively. Using the software Signal P, we predicted signal peptides for 12.95% and 35.60% of the proteins identified in the exponential and stationary phases, respectively, which could therefore be secreted by the Sec pathway. For the exponential growth phase, we found in abundance proteins like the ribosomal proteins, toxins and proteins belonging to the group "defence mechanisms". For the stationary growth phase, we found that the most abundant proteins were those with unknown function, and in many of these we identified characteristic domains of proteases and peptidases.ConclusionsOur study provided the first dataset of the secretome of R. etli and its modifications, which may lead to novel insights into the adaptive response of different stages of growth. In addition, we found a high number of proteins with unknown function; these proteins could be analyzed in future research to elucidate their role in the extracellular proteome of R. etli.

Proteomic Evidences for Rex Regulation of Metabolism in Toxin-Producing Bacillus cereus ATCC 14579

“…We assume that cell lysis cannot account for changes in the abundance level of these cytoplasmic proteins since: (i) cell viability count did not change (data not shown), (ii) EF-Tu did not accumulate in extracellular medium (Table S7, [63]), and (iii) the abundance pattern of cytoplasmic proteins was dependent on growth conditions and did not always correlate with intracellular abundance changes (Table 2 and 4). Among the cytoplasmic proteins identified in B. cereus exoproteome, several have already been identified in the exoproteome of other bacteria, and many have been described as extracellular moonlighting components playing a role in bacterial virulence [64], [65].…”

Annexin A1, Annexin A2, and Dyrk 1B are upregulated during GAS1‐induced cell cycle arrest

“…Peptides were identified using a 3200 QTRAP LC‐MS/MS System (Applied Biosystems/MDS Sciex, San Francisco, CA) equipped with a nanoelectrospray ion source (NanoSpray II) and a MicroIonSpray II head, and coupled to a nanoAcquity Ultra Performance LC system (Waters Corporations, Milford, MA). Peptides were processed and analyzed in the Analytical Unit, Facultad de Medicina, UNAM, as previously described (Meneses, Mendoza‐Hernández, & Encarnación, ).…”

MMBL proteins: from lectin to bacteriocin

“…Sequencebased clustering of several of the corresponding fused MMBL domains indicates evolutionary relatedness, despite their occurrence in taxonomically unrelated prokaryotic genera: associated domains include subtilase (subtilisin-like serine protease) in Burkholderia and Stigmatella (Betaproteobacteria and Deltaproteobacteria respectively), unspecified hydrolase (GDSL-like lipase/acylhydrolase) in Granulicella and Terriglobus (Acidobacteria), trypsin-like protease and NlpC/P60-type cysteine peptidase in Streptomyces and Cellulomonas respectively (both Actinobacteria). The trypsin-related MMBL proteins are equipped with an additional C-terminal module potentially involved in adhesion (β-propeller VCBS domain [39]) or sugar-binding (ricin-type β-trefoil lectin). The trypsin-related MMBL proteins are equipped with an additional C-terminal module potentially involved in adhesion (β-propeller VCBS domain [39]) or sugar-binding (ricin-type β-trefoil lectin).…”