IDENTIFICATION AND CO-OCCURRENCE OF DEFENSE SYSTEMS IN THE SHEWANELLA PANGENOME

SANHUEZA SALAS, LUIS FRANCISCO; CERBINO GABRIELA N.; AYALA NUÑEZ, TEOLINCACIHUATL; RAMIREZ, MARÍA SOLEDAD; QUIROGA, CECILIA

CHAPADMALAL - BUENOS AIRES

Congreso; XVIII CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL - SAMIGE 2023; 2023

SAMIGE

Defense systems (DS) protect bacteria against the attack of mobile genetic elements, suchas phages and plasmids, ensuring their survival. In recent years a wide variety of new DShave been discovered expanding considerably the current knowledge in the field. Theanalysis of their genetic localization revealed that can be grouped in the same region of agenome forming defense islands or hotspots. The aim of this work was to identify the DS inthe Shewanella genus, a non-fermenting gram-negative rod that thrives in aquatic nichesand causes infections in humans. In addition, we evaluated whether there was anassociation between DS and the host habitat. Complete and draft Shewanella spp. genomesavailable from Genbank until July 2023 were included in the analysis (n= 431). All genomeswere organized based on their average nucleotide identity (ANI) value using FastANI andvisualized using the rplot command from RStudio. Information regarding the source ofisolation was also included in the analysis. DS families were identified using the toolPADLOC v1.1.0., and potential defense hotspots were detected by comparative genomeanalysis using Mauve v2 and ACT v18.1.0 tools. We detected 98 DS families distributedheterogeneously throughout all species. The most frequent families corresponded torestriction-modification (RM) (645), DMS (DNA modification systems; 274), dXTPases (218)and CRISPR-Cas (220). We also observed that some DS families were highly diversifiedwithin this genus, i.e., CRISPR-Cas (10 subtypes), Abi (abortive infection system; 14), andRetron (a reverse transcriptase-based system; 11). On the other hand, some DS showed aconsiderable occurrence within individual species, such as Abi (29), CBASS (22), Gabija(22,) and Retron (21) in Shewanella algae; Abi (56), Mokosh (29), SoFic (29) and Lamassu(25) in Shewanella baltica; and Abi (34),Mokosh (33), SoFic (29) and CBASS (18) inShewanella xiamenensis; showing a few differences at species level. Colocalization andcomparative analyses revealed that some DS coexist in a specific hotspot, as seen for theclinical isolate Shewanella sp. Shew256, which contained two putative defense islands. Thefirst one harboring the systems type-I RM with AbiD and the second one with systems SoFic,type-V RM and DMS. Similarly, the environmental isolate S. frigidimarina Ag06-30 encodeda type-I RM, a DMS, and Zorya systems at the same hotspot, which reveals the plasticity ofeach defense island. Lastly, we observed that most Mokosh and SoFic systems were foundfrequently in aquatic and animal-related hosts, which corresponded mainly to S. baltica andS. xiamenensis isolates, but sporadically in clinical isolates (predominantly S. algae). Ouranalysis reveals that Shewanella spp. adapts to the environment by acquiring and employingseveral DS systems. This adaptation is probably shaped by the encounter between eachhost and the foreign mobile elements present in an ecosystem.