Identification of Streptomyces coelicolor Proteins That Are Differentially Expressed in the Presence of Plant Material

Abstract

Streptomyces coelicolor and Lemna minor were used as a model to study the modulation of bacterial gene expression during plant-streptomycete interactions. S. coelicolor was grown in minimal medium with and without L. minor fronds. Bacterial proteomes were analyzed by two-dimensional gel electrophoresis, and a comparison of the two culture conditions resulted in identification of 31 proteins that were induced or repressed by the presence of plant material. One-half of these proteins were identified by peptide mass fingerprinting by using matrix-assisted laser desorption ionization-time of flight mass spectrometry. The induced proteins were involved in energetic metabolism (glycolysis, pentose phosphate pathway, oxidative phosphorylation), protein synthesis, degradation of amino acids, alkenes, or cellulose, tellurite resistance, and growth under general physiological or oxidative stress conditions. The repressed proteins were proteins synthesized under starvation stress conditions. These results suggest that root exudates provide additional carbon sources to the bacteria and that physiological adaptations are required for efficient bacterial growth in the presence of plants.Plant rhizospheres harbor diverse communities of microorganisms. It is generally assumed that rhizosphere microbes use compounds released by the plant roots as their major nutrient sources. This ability is the nutritional basis of rhizosphere competence (32). Streptomycetes are gram-positive bacteria that are frequently isolated from terrestrial plant rhizospheres (3, 15), but Wohl and McArthur (49) also showed that streptomycetes are associated with freshwater plants. Until now, few research efforts have been dedicated to the study of plantstreptomycete interactions, and most previous efforts have involved the common scab-inducing streptomycetes and their host plants (29). As several Streptomyces species have been shown to be effective biocontrol agents for plant diseases (10), studies on the interactions between saprophytic streptomycetes and plants need to be documented more.We propose Streptomyces coelicolor and Lemna minor as an experimental model to study the modulation of bacterial gene expression during the interaction between a saprophytic streptomycete and a plant. Recent research in our laboratory has shown that L. minor, a small aquatic plant extensively used in bioremediation (38) and environmental studies (30), is colonized by various Streptomyces species (unpublished data). On the other hand, S. coelicolor is a common inhabitant of plant rhizospheres (11) that can be readily cocultivated in the presence of L. minor under sterile conditions. The fact that the S. coelicolor chromosome (6) has been fully sequenced is an important asset in proteomic studies.Proteomics has become an integral part of gene expression analysis. The functional complement of genetic information can be analyzed by a combination of two-dimensional gel electrophoresis for the separation of complex mixtures of proteins and mass spectrometry for identification...

Streptomyces coelicolor Encodes a Urate-Responsive Transcriptional Regulator with Homology to PecS from Plant Pathogens

“…Both streptomycetes that inhabit the rhizosphere as well as endophytic species have been shown to prime plants against pathogens, reflecting induction of defense systems in the plant (44). Conversely, analysis of the S. coelicolor proteome after exposure to plant exudates shows differential expression of several proteins, including proteins required for utilization of specific carbon sources and proteins involved in stress adaptation, such as super- oxide dismutase (45). We speculate that the oxidative stress response induced in S. coelicolor upon exposure to plant material includes detection of plant-derived urate.…”

Phylogenetic Distribution of Potential Cellulases in Bacteria

“…Indeed, the plant cell wall deconstruction, as a whole, is considered a complex process requiring many enzymes. Their expression is assumed to be a response to the availability of specific substrates (44,47).…”

Gut and Root Microbiota Commonalities

“…Genes involved in root exudate usage, root attachment, and survival are induced in bacteria colonizing roots (120,121). In vitro expression technology (IVET) (122), proteomic analysis, microarray and RNA Seq transcriptomics, and genetic analysis have revealed rhizobial (120,121,123), Pseudomonas (124,125), Streptomyces (126), and other bacterial genes expressed on roots or rhizospheres. Similarly, bacteria may differentially express genes when in guts.…”