Summary The unicellular alga Chlamydomonas reinhardtii and the bacterium Pseudomonas protegens serve as a model to study the interactions between photosynthetic and heterotrophic microorganisms. P . protegens secretes the cyclic lipopeptide orfamide A that interferes with cytosolic Ca 2+ homeostasis in C . reinhardtii resulting in deflagellation of the algal cells. Here, we studied the roles of additional secondary metabolites...

Summary Bulk soil and rhizosphere are soil compartments selecting different microbial communities. However, it is unknown whether this selection also can change the genome content of specific bacterial taxa, splitting a population in distinct ecotypes. To answer this question we compared the genome sequences of 53 isolates obtained from sugarcane rhizosphere (28) and bulk soil (25). These isolates were previously classified in...

Summary Pseudomonas is a large and diverse genus of Gammaproteobacteria . To provide a framework for discovery of evolutionary and taxonomic relationships of these bacteria, we compared the genomes of type strains of 163 species and 3 additional subspecies of Pseudomonas , including 118 genomes sequenced herein. A maximum likelihood phylogeny of the 166 type strains based on protein sequences of 100 single‐copy orthologous gen...

Summary Fluorescent Pseudomonas spp. are widely studied for their beneficial activities to plants. To explore the genetic diversity of Pseudomonas spp. in tropical regions, we collected 76 isolates from a Brazilian soil. Genomes were sequenced and compared to known strains, mostly collected from temperate regions. Phylogenetic analyses classified the isolates in the P. fluorescens (57) and P. putida (19) groups. Among the isol...

Summary Many microorganisms compete for extracellular iron using strain‐specific chelators known as siderophores. The ferric‐siderophore complex limits local access to iron because import requires a suitable cognate receptor. Interestingly, many species carry receptors that enable ‘cross‐feeding’ on heterologous siderophores made by neighboring organisms, although little is known about how this ubiquitous behaviour is regulate...

Summary Pseudomonas protegens strain Pf‐5 is a soil bacterium that was first described for its capacity to suppress plant diseases and has since been shown to be lethal to certain insects. Among these is the common fruit fly Drosophila melanogaster , a well‐established model organism for studies evaluating the molecular and cellular basis of the immune response to bacterial challenge. Pf‐5 produces the insect toxin FitD, but a...

Summary Swarming motility is a flagella‐driven multicellular behaviour that allows bacteria to colonize new niches and escape competition. Here, we investigated the evolution of specific mutations in the GacS/GacA two‐component regulatory system in swarming colonies of Pseudomonas protegens Pf‐5. Experimental evolution assays showed that repeated rounds of swarming by wildtype Pf‐5 drives the accumulation of gacS/gacA spontane...

Summary Bacteria can be both highly communicative and highly competitive in natural habitats and antibiotics are thought to play a role in both of these processes. The soil bacterium P seudomonas protegens Pf‐5 produces a spectrum of antibiotics, two of which, pyoluteorin and 2,4‐diacetylphloroglucinol ( DAPG ), function in intracellular and intercellular communication, both as autoinducers of their own production. Here, we de...

Summary Gene expression profiles of the biological control strain P seudomonas protegens Pf ‐5 inhabiting pea seed surfaces were revealed using a whole‐genome oligonucleotide microarray. We identified genes expressed by Pf ‐5 under the control of two global regulators ( GacA and RpoS ) known to influence biological control and secondary metabolism. Transcript levels of 897 genes, including many with unknown functions as well a...

Summary Zinc is an important nutrient but can be lacking in some soil environments, influencing the physiology of soil‐dwelling bacteria. Hence, we studied the global effect of zinc limitation on the transcriptome of the rhizosphere biocontrol strain Pseudomonas protegens Pf ‐5 (formerly Pseudomonas fluorescens ). We observed that the expression of the putative zinc uptake regulator ( Z ur) gene was upregulated, and we mapped...

Summary The GacS/GacA signal transduction system is a central regulator in Pseudomonas spp., including the biological control strain P. fluorescens Pf‐5, in which GacS/GacA controls the production of secondary metabolites and exoenzymes that suppress plant pathogens. A whole genome oligonucleotide microarray was developed for Pf‐5 and used to assess the global transcriptomic consequences of a gacA mutation in P. fluorescens Pf...

Summary Pseudomonas fluorescens CHA0 and the related strain Pf‐5 are well‐characterized representatives of rhizosphere bacteria that have the capacity to protect crop plants from fungal root diseases, mainly by releasing a variety of exoproducts that are toxic to plant pathogenic fungi. Here, we report that the two plant‐beneficial pseudomonads also exhibit potent insecticidal activity. Anti‐insect activity is linked to a nove...