Colonization of the halophyte Salicornia europaea L. by human pathogenic microorganisms alters the plant's transcriptomic profile in vitro

Salicornia europaea L. is a halophyte used for many industrial purposes and can also be consumed as a raw vegetable. It is well known that vegetables can become contaminated by human pathogenic microorganisms (HPMOs) during cultivation, e.g., through contaminated soil or water. There are many reports about outbreaks of infections linked to various vegetables. Although S. europaea tissue extracts have antimicrobial properties, the ability of this plant to be colonized by HPMOs has never been studied.

The main objective of our work was to study the susceptibility of S. europaea to colonization by HPMOs under different salinity conditions and to identify possible plant host defence responses to such infections.

S. europaea was cultivated under sterile conditions and inoculated with three bacterial strains: Escherichia coli, Salmonella enterica, and Listeria monocytogenes. Four weeks after inoculation, 2000 plants were collected for further analysis: (i) assessment of the plants' growth parameters; (ii) determination of the total bacteria and HPMO abundance in the shoots and roots using culture-dependent and -independent (qPCR) methods; and (iii) a comparative analysis of the transcriptomic profiles.

The obtained results revealed significant differences in the plants' growth parameters between the control and the treatments inoculated with different HPMOs. Moreover, it was shown that the rhizosphere and plant organs can harbor complex microbial communities, which may be involved in regulating or eliminating the occurrence of HPMOs. The transcriptomic analyses revealed differentially expressed genes only in response to some of the HPMOs tested.

In conclusion, the presence of HPMOs in S. europaea can be attributed to the plant's differential gene expression in response to bacteria, as well as the potential role of the plant's endophytic community in regulating host colonization by HPMOs.

Funding:

This research was conducted as a part of the SaliFood project funded by the National Science Centre (NCN, Poland) (UMO-2019/33/B/NZ9/02803).