Radiotolerant endophytic bacteria and analysis of the effects of 137Cesium on the metabolome of Pantoea sp

Abstract

Some bacteria have developed mechanisms to withstand the stress caused by ionizing radiation. The ability of these radioresistant microorganisms to survive high levels of radiation is primarily attributed to their DNA repair mechanisms and the production of protective metabolites. To determine the effect of irradiation on bacterial growth, we propose to compare the metabolites produced by the irradiated isolates to those of the control (non-irradiated isolates) using mass spectrometry, molecular networking, and chemometric analysis. We identified the secondary metabolites produced by these bacteria and observed variations in growth following irradiation. Notably, after 48 h of exposure to radiation, Pantoea sp. bacterial cells exhibited a significant 6-log increase compared to non-irradiated cells. Non-irradiated cells produce exclusively Pyridindolol, 1-hydroxy-4-methylcarbostyril, N-alkyl, and N-2-alkoxyethyl diethanolamine, while 5'-methylthioadenosine was detected only in irradiated cells. These findings suggest that the metabolic profile of Pantoea sp. remained relatively stable. The results obtained from this study have the potential to facilitate the development of innovative strategies for harnessing the capabilities of endophytic bacteria in radiological protection and bioremediation of radionuclides.

Keywords: Endophytic bacteria, Radiotolerance; Gamma radiation; Metabolome; Molecular networking.

Fig. 1

Test of sensitivity to ionizing radiation using a 96-well microdilution plate

Fig. 2

Molecular Networking containing the main molecular families identified in the de-replication analysis of Pantoea sp. ELP04 using GNPS platform. Nodes with black border: substances annotated by GNPS. Nodes with gray color border: substances identified based on spectral similarities, fragmentation profile, and literature. In Blue: Pantoea sp. non-irradiated (ethyl acetate); Yellow: Pantoea sp. irradiated (ethyl acetate); Purple: Pantoea sp. non-irradiated (methanol); Orange: Pantoea sp. irradiated (methanol)

Fig. 3

Principal Component Analysis (PCA) of the extracts’ spectral data produced by bacterial cells exposed and not exposed to radiation. In (A) positive ionization mode and in (B) negative ionization mode. F1 = culture medium only with no microbial inoculum, F2 = bacteria non-irradiated, and F3 = irradiated bacteria for 48 h

Fig. 4

Heatmap for positive ionization mode (A) and negative ionization mode (B). F1 = culture medium only with no microbial inoculum, F2 = non-irradiated bacteria, and F3 = irradiated bacteria for 48 h. The greater the intensity for a detected ion, the redder the tone. In contrast, the smaller the intensity, the bluer the tone