Thorsellia dominance and bacterial community structure in two major malaria vectors: an exploratory study in Northwestern Argentina.

Malaria continues to be one of the major global health burdens despite worldwide efforts to reduce its incidence and prevalence. Recent technological advances have generated new mosquito-control alternatives, one of which involves the use of symbionts that are part of the core gut microbiota to develop paratransgenesis strategies. This exploratory study characterized the bacterial community of Anopheles argyritarsis and Anopheles pseudopunctipennis across three environments: Iruya River (mountain forest), Conchas River (transitional zone), and Chirimayo River (agricultural landscape). Through 16S rRNA gene sequencing, we obtained 1,308 amplicon sequence variants (ASVs). We registered dominance of the phyla Proteobacteria (94%) and Bacteroidota (3.28%). At the genus level, Thorsellia was the dominant taxon within the core microbiota (71.5%). Shannon (5.09-5.95) and Simpson (0.988-0.996) diversity indices indicated that, despite the increase of multiple bacterial genera in anthropized areas, community evenness remained balanced. Meanwhile, beta diversity analysis (Bray-Curtis) demonstrated that both host species and sampling area influenced bacterial composition. These results are presented within a descriptive and exploratory framework due to the limited replication across species-locality combinations. Despite the challenge of establishing host-symbiont relationships, Thorsellia is a genus that warrants further tracking across different developmental stages based on its notable stability in this study. Under the holobiont perspective, understanding how the microbiota influences vector fitness, longevity, and resilience will help guide different efforts toward control and surveillance strategies across ecological settings for future investigations. Although Argentina has not reported autochthonous malaria cases, the vector persists and the risk of re-emergence remains latent.