Paenibacillus polymyxa Invades Plant Roots and Forms Biofilms

Abstract

Paenibacillus polymyxa is a plant growth-promoting rhizobacterium with a broad host range, but so far the use of this organism as a biocontrol agent has not been very efficient. In previous work we showed that this bacterium protects Arabidopsis thaliana against pathogens and abiotic stress (S. Here, we studied colonization of plant roots by a natural isolate of P. polymyxa which had been tagged with a plasmid-borne gfp gene. Fluorescence microscopy and electron scanning microscopy indicated that the bacteria colonized predominantly the root tip, where they formed biofilms. Accumulation of bacteria was observed in the intercellular spaces outside the vascular cylinder. Systemic spreading did not occur, as indicated by the absence of bacteria in aerial tissues. Studies were performed in both a gnotobiotic system and a soil system. The fact that similar observations were made in both systems suggests that colonization by this bacterium can be studied in a more defined system. Problems associated with green fluorescent protein tagging of natural isolates and deleterious effects of the plant growth-promoting bacteria are discussed.TimmuskPaenibacillus polymyxa (previously Bacillus polymyxa) is one of many plant growth-promoting rhizobacteria (PGPR) and is known to have a broad host plant range. It has been isolated from the rhizospheres of wheat and barley (30), white clover, perennial ryegrass, crested wheatgrass (19), lodgepole pine (18), Douglas fir (43), green bean (37), and garlic (24). In addition to several P. polymyxa antagonistic effects reported previously, we have shown that P. polymyxa antagonizes oomycetic pathogens (49). Due to its broad host range, its ability to form endospores, and its ability to produce different kinds of antibiotics, P. polymyxa is a potential commercially useful biocontrol agent. So far, most studies on the biocontrol activity of P. polymyxa have concentrated on the production of different antibiotic substances. Although biocontrol in general has been used for decades, its application has not been very consistent, perhaps due in part to an incomplete understanding of the biological control system (14, 15). Plant roots are not passive targets for soil organisms. Therefore, in addition to understanding the agent itself and its interaction with the pathogen, knowledge of the interaction of the biological control agent with the plant root is required. Although the plant growthpromoting activity of P. polymyxa has been the subject of numerous studies (references 2, 3, and 53 and references therein), the pattern of colonization of this bacterium on host plants has not been studied in detail previously.We previously reported that a natural isolate of P. polymyxa induces drought tolerance and antagonizes pathogens in Arabidopsis thaliana. These effects were observed with a gnotobiotic system and with soil (48, 49). These studies indicated that, aside from the beneficial effects observed, inoculation of A. thaliana by P. polymyxa (in the absence of biotic or abiotic stress) resulted in a ...

Effect of some plant growth-promoting rhizobacteria strains on root-knot nematode, Meloidogyne incognita, on tomatoes

“…reduced the rate of egg hatching and J2 number Data are means of 10 replications; means, followed by the same letter within a column, are not different according to Duncan's multiple-range test (P ≤ 0.05) of M. javanica, M. hapla, M. incognita, M. enterolobii, M. chitwoodi, and M. fallaxin vitro (Bakengesa, 2016). These results may be attributed to bacterial products such as antibiotics and secondary metabolites (Timmusk et al, 2005). Similarly, the study of Son et al (2009) showed that among 40 strains of Paenibacillus spp.…”

Substrate utilization by endophytic bacteria Paenibacillus polymyxa P2b-2R that may facilitate bacterial entrance and survival inside diverse plant hosts

“…Paenibacillus polymyxa is an endospore-forming, non-pathogenic bacterium readily found in environments such as plant roots, soil, and marine sediments (Timmusk et al 2005;Ravi et al 2007). Bal et al (2012) successfully isolated several Paenibacillus strains that possess significant acetylene-reduction activity (N-fixing capacity) from the extracts of surface-sterilized lodgepole pine seedling and tree tissues.…”

Isolation, Characterization and Identification of Phosphate- and Potassium- Solubilizing Bacteria from Weathered Materials of Granite Rock Mountain, That Son, an Giang Province, Vietnam

“…It can produce IAA, nitrogen fixation, P and Zn solubilization. Paenibacillus polymyxa (prevoiously Bacillus polymyxa) is one of many plant growth-promoting rhizobacteria and it was known to have a broad host plant range [38].…”