In vitro Trypanocidal Activity, Genomic Analysis of Isolates, and in vivo Transcription of Type VI Secretion System of Serratia marcescens Belonging to the Microbiota of Rhodnius prolixus Digestive Tract

Abstract

Serratia marcescens is a bacterium with the ability to colonize several niches, including some eukaryotic hosts. S. marcescens have been recently found in the gut of hematophagous insects that act as parasite vectors, such as Anopheles, Rhodnius, and Triatoma. While some S. marcescens strains have been reported as symbiotic or pathogenic to other insects, the role of S. marcescens populations from the gut microbiota of Rhodnius prolixus, a vector of Chagas’ disease, remains unknown. Bacterial colonies from R. prolixus gut were isolated on BHI agar. After BOX-PCR fingerprinting, the genomic sequences of two isolates RPA1 and RPH1 were compared to others S. marcescens from the NCBI database in other to estimate their evolutionary divergence. The in vitro trypanolytic activity of these two bacterial isolates against Trypanosoma cruzi (DM28c clone and Y strain) was assessed by microscopy. In addition, the gene expression of type VI secretion system (T6SS) was detected in vivo by RT-PCR. Comparative genomics of RPA1 and RPH1 revealed, besides plasmid presence and genomic islands, genes related to motility, attachment, and quorum sensing in both genomes while genes for urea hydrolysis and type II secretion system (T2SS) were found only in the RPA1 genome. The in vitro trypanolytic activity of both S. marcescens strains was stronger in their stationary phases of growth than in their exponential ones, with 65–70 and 85–90% of epimastigotes (Dm28c clone and Y strain, respectively) being lysed after incubation with RPA1 or RPH1 in stationary phase. Although T6SS transcripts were detected in guts up to 40 days after feeding (DAF), R. prolixus morbidity or mortality did not appear to be affected. In this report, we made available two trypanolytic S. marcescens strains from R. prolixus gut to the scientific community together with their genomic sequences. Here, we describe their genomic features with the purpose of bringing new insights into the S. marcescens adaptations for colonization of the specific niche of triatomine guts. This study provides the basis for a better understanding of the role of S. marcescens in the microbiota of R. prolixus gut as a potential antagonist of T. cruzi in this complex system.

Influence of Serratia marcescens and Rhodococcus rhodnii on the Humoral Immunity of Rhodnius prolixus

“…In this sense, the gut bacterial microbiota impacts the development of trypanosomatids in insects [17][18][19]. In R. prolixus, the intestinal microbiota components identified to date are Serratia, Dietzia, Gordonia, Mycobacterium, Corynebacterium, Rhodococcus, Pectobacterium, and Staphylococcus [17,[20][21][22][23][24]. However, knowledge of the interaction between the triatomine and the T. cruzi with the bacterial species Rhodococcus rhodnii and Serratia marcescens is still scarce [17,18,23].…”

The Role of Bacterial Symbionts in Triatomines: An Evolutionary Perspective

“…The numbers of T. cruzi in aposymbiotic insects are ten times higher than in insects with a normal microbiota [247]. Some strains of Serratia marcescens, have direct trypanolytic activity [192,247,256,257], but this again only affects some T. cruzi strains as S. marcescens has been found in wild caught triatomines infected with T. cruzi [234,242,244,258]. Furthermore, in feral triatomines naturally infected with T. cruzi, there is an overrepresentation and subrepresentation of some Actinomycetes and Proteobacteria, but whether this helps or hinders T. cruzi infections remains to be addressed [234,241,245].…”

“…marcescens has been found in wild caught triatomines infected with T . cruzi [ 234 , 242 , 244 , 258 ]. Furthermore, in feral triatomines naturally infected with T .…”

Proteome of the Triatomine Digestive Tract: From Catalytic to Immune Pathways; Focusing on Annexin Expression

“…Serratia marcescens , is a Gram-negative bacteria that compose R. prolixus microbiota ( Azambuja et al, 2004 ; Vieira et al, 2016 ). Recently, it was identified that S. marcescens strains from R. prolixus gut presented many virulence factors ( da Mota et al, 2019 ), as already described in other S. marcescens strains, including pore-forming toxins, such as hemolysins, which potentially cause damages to epithelial cells ( Hertle, 2000 , 2005 ; Ochieng et al, 2014 ; Lee et al, 2016 ). In D. melanogaster , it has been shown that S. marcescens infection induces gut damage and inflammatory reactions ( Lee et al, 2016 ).…”