Insects as alternative hosts for phytopathogenic bacteria

Abstract

Phytopathogens have evolved specialized pathogenicity determinants that enable them to colonize their specific plant hosts and cause disease, but their intimate associations with plants also predispose them to frequent encounters with herbivorous insects, providing these phytopathogens with ample opportunity to colonize and eventually evolve alternative associations with insects. Decades of research have revealed that these associations have resulted in the formation of bacterial-vector relationships, in which the insect mediates dissemination of the plant pathogen. Emerging research, however, has highlighted the ability of plant pathogenic bacteria to use insects as alternative hosts, exploiting them as they would their primary plant host. The identification of specific bacterial genetic determinants that mediate the interaction between bacterium and insect suggests that these interactions are not incidental, but have likely arisen following the repeated association of microorganisms with particular insects over evolutionary time. This review will address the biology and ecology of phytopathogenic bacteria that interact with insects, including the traditional role of insects as vectors, as well as the newly emerging paradigm of insects serving as alternative primary hosts. Also discussed is one case where an insect serves as both host and vector, which may represent a transitionary stage in the evolution of insect-phytopathogen associations.

Insect pathogenicity in plant-beneficial pseudomonads: phylogenetic distribution and comparative genomics

“…In general, fluorescent pseudomonads might be quite ubiquitous and probably possess an arsenal of traits allowing them to easily switch niches and to conquer the habitat they encounter. Insects could be especially useful as a means of dispersal, a phenomenon documented for diverse plant-pathogenic bacteria (Nadarasah and Stavrinides, 2011). Some Pseudomonas syringae strains for instance can use the pea aphid as alternative primary host where they replicate to high numbers and can be deposited onto a new plant host via excreted honeydew (Stavrinides et al, 2009).…”

The Role of Secretion Systems and Small Molecules in Soft-Rot Enterobacteriaceae Pathogenicity

“…Only recently have we appreciated that numerous bacterial plant pathogens are vectored by insects (110), and this suggests that the search for methods that interfere with insect attraction to diseased plants or bacterial uptake will be fruitful in the search for bacterial disease-control strategies.…”

The influence of the accessory genome on bacterial pathogen evolution

“…109 For example, pathogens may be exposed to a variety of bacteriophages [e.g., vibriophages], 52 and they frequently encounter other organisms that may act as alternative hosts and have resident microbial populations. 110 Moreover, several virulence genes in human pathogens have been experimentally determined to provide resistance to grazing protozoa 111,112 or to kill amoeba associated with them in biofilms. 113 It has even been proposed that some virulence genes of human pathogens originally evolved as resistance mechanisms to protozoa [111][112][113] and Brüssow 33 goes so far as to propose that lysogeny itself evolved as an alliance between bacteria and phages "to fight grazing protists".…”