Functional Role of Bacteria from Invasive Phragmites australis in Promotion of Host Growth

Abstract

We hypothesize that bacterial endophytes may enhance the competitiveness and invasiveness of Phragmites australis. To evaluate this hypothesis, endophytic bacteria were isolated from P. australis. The majority of the shoot meristem isolates represent species from phyla Firmicutes, Proteobacteria, and Actinobacteria. We chose one species from each phylum to characterize further and to conduct growth promotion experiments in Phragmites. Bacteria tested include Bacillus amyloliquefaciens A9a, Achromobacter spanius B1, and Microbacterium oxydans B2. Isolates were characterized for known growth promotional traits, including indole acetic acid (IAA) production, secretion of hydrolytic enzymes, phosphate solubilization, and antibiosis activity. Potentially defensive antimicrobial lipopeptides were assayed for through application of co-culturing experiments and mass spectrometer analysis. B. amyloliquefaciens A9a and M. oxydans B2 produced IAA. B. amyloliquefaciens A9a secreted antifungal lipopeptides. Capability to promote growth of P. australis under low nitrogen conditions was evaluated in greenhouse experiments. All three isolates were found to increase the growth of P. australis under low soil nitrogen conditions and showed increased absorption of isotopic nitrogen into plants. This suggests that the Phragmites microbes we evaluated most likely promote growth of Phragmites by enhanced scavenging of nitrogenous compounds from the rhizosphere and transfer to host roots. Collectively, our results support the hypothesis that endophytic bacteria play a role in enhancing growth of P. australis in natural populations. Gaining a better understanding of the precise contributions and mechanisms of endophytes in enabling P. australis to develop high densities rapidly could lead to new symbiosis-based strategies for management and control of the host.

Contrasting Patterns in Diversity and Community Assembly of Phragmites australis Root-Associated Bacterial Communities from Different Seasons

“…3; Fig. S3; Table S2), consistent with previous studies (22,30,(47)(48)(49). We selected the significantly different abundant genera influenced by seasons and compartments and found that some of these groups were related to specific functions.…”

Invasive Lactuca serriola seeds contain endophytic bacteria that contribute to drought tolerance

“…Soil microbiota in the introduced habitats have been postulated as a major source of mutualistic microorganisms, but our results suggest that seed endophytic bacteria might be another source. Microorganisms within seeds of alien plants can disperse with the plant germplasm to novel habitats, and at least some of them, like K. cowanii in this study, might be able to promote the plant performance 18 – 20 . Seed endophytic bacteria, similar to the soil microbiota, might influence the invasive dynamics of alien plants.…”

“…However, it should be noted that seed endophytic bacteria can disperse along with the host plants 17 . It is possible that seed endophytic bacteria improve the fitness of invasive plants, similar to the bacteria occurring in the rhizosphere or leaves 18 – 20 . Invasive plants might benefit from seed endophytic bacteria instead of bacteria in the introduced habitats for their successful establishment.…”

Seed‐vectored endophytic bacteria modulate development of rice seedlings

“…; Soares et al . ). Rhizophagy (root consumption of microbes) is a mechanism of nutrient transport to plants from soil via microbes in which microbes become intracellular in root cells and are degraded (Paungfoo‐Lonhienne et al .…”