Biology subjects

Pais, I. S.

Publications and source records attributed to Pais, I. S..

3 recordsLinked to original sources

bioRxiv2021

A prior exposure to Serratia marcescens or xenobiotics primes Drosophila enterocytes against a recurring cytoplasmic purge

The cytoplasmic extrusion of enterocytes is a fast response to an exposure to pore-forming toxin (PFT)-producing bacteria whereby their apical cytoplasm is extruded into the intestinal lumen. As a result of this purge, the intestinal epithelium becomes thin prior to a subsequent recovery. We report here that the ingestion of ethanol or caffeine induces a similar response, which suggests that a common purging process is triggered by bacterial toxins and abiotic toxicants. We also delineate an additional mechanism that is initiated by these stimuli that we refer to as priming. The initial exposure of the intestinal epithelium to either PFT or xenobiotics protects enterocytes against a further round of purging upon a second bacterial infection. Priming prevents the epithelium from being persistently thin in the context of chronic intestinal infections. We have identified the upper part of the p38b MAPK pathway as well as the homeobox-containing transcription factors E5/EMS as being required for priming and not for the regrowth of enterocytes after the cytoplasmic purge. Unexpectedly, the priming process appears to function cell-nonautonomously. Our findings suggest that the cytoplasmic purge extrusion has been selected because it constitutes a fast reaction to accidental exposure to bacterial toxins or toxicants.

physiology↗

bioRxiv2021

The amino acid transporter CG1139 is required for retrograde transport and fast recovery of gut enterocytes after Serratia marcescens intestinal infection

The intestinal tract is constantly exposed to microbes. Severe infections can arise following the ingestion of pathogenic microbes from contaminating food or water sources. The host directly fights off ingested pathogens with resistance mechanisms, the immune response, or withstands and repairs the damages inflicted either by virulence factors or the host immune effectors, through tolerance/resilience mechanisms. In a previous study, we reported the existence in Drosophila melanogaster of a novel evolutionarily conserved resilience mechanism to intestinal infections with a hemolysin-positive Serratia marcescens strain (SmDb11), the purge of the apical cytoplasm of enterocytes. The epithelium becomes very thin and recovers rapidly, regaining its normal thickness within several hours. Here, we found that this recovery of gut enterocyte morphology is based on the host internal reserves and not on ingested food. Indeed, we observed a retrograde transport of amino acids from the host hemolymph to the enterocytes. We have identified several amino acid transporters required for recovery and we focused on the SLC36 family transporter CG1139. CG1139 is required for the retrograde transport of amino acids. RNA sequencing revealed that genes involved in the positive regulation of growth were observed in wild-type but not CG1139 mutant guts, in which the expression of Myc and genes involved in Insulin signaling is down-regulated. Functional analysis revealed that Myc is also required for the recovery of the thick gut epithelium after infection. Altogether, our results show the importance of an amino acid transporter in the fast regrowth of the enterocytes upon infection. Unexpectedly, we found that this transporter acts non cell-autonomously and can regulate the transcription of other genes, suggesting a signaling function of CG1139 that therefore appears to act as a transceptor.

physiology↗

bioRxiv2018

Drosophila melanogaster establishes a species-specific mutualistic interaction with stable gut-colonizing bacteria

Animals live together with diverse bacteria that can impact their biology. In Drosophila melanogaster, gut-associated bacterial communities are relatively simple in composition but also have a strong impact on host development and physiology. However, it is still unknown if bacteria can proliferate and stably associate with the gut of D. melanogaster. In fact, it is generally assumed that bacteria are transient and their constant ingestion with food is required to maintain their presence in the gut. Here, we identify bacterial species from wild-caught D. melanogaster that stably associate with the host independently of continuous inoculation. Moreover, we show that specific Acetobacter wild isolates can proliferate in the gut. We further demonstrate that the interaction between D. melanogaster and the wild isolated Acetobacter thailandicus is mutually beneficial and that the stability of the gut association is key to this mutualism. The stable population in the gut of D. melanogaster allows continuous bacterial spreading into the environment, which is advantageous to the bacterium itself. The bacterial dissemination is in turn advantageous to the host since the next generation of flies develops in the presence of this particularly beneficial bacterium. Ac. thailandicus leads to a faster host development and higher fertility of emerging adults, when compared to other bacteria isolated from wild-caught flies. Furthermore, Ac. thailandicus is sufficient and advantageous when D. melanogaster develops in axenic or freshly collected figs, respectively. This isolate of Ac. thailandicus colonizes several genotypes of D. melanogaster but not of the closely related Drosophila simulans, indicating that the stable association is host specific. This work establishes a new conceptual model to understand D. melanogaster- gut microbiota interactions in an ecological context; stable interactions can be mutualistic through microbial farming, a common strategy in insects. Moreover, these results develop the use of D. melanogaster as a model to study gut microbiota proliferation and colonization.\n\nAuthor summaryAnimals, including humans, live together with complex bacterial communities in their gut that influence their physiology and health. The fruit fly Drosophila melanogaster has been an excellent model organism to study host-microbe interactions and harbours a relative simple gut bacterial community. However, it is not known which of these bacteria can proliferate and form stable communities in the gut, and the current hypothesis is that these bacteria are only transiently associated with the gut. Here, we show that in D. melanogaster collected from a natural population stable gut bacteria do exist. We isolated specific species that can proliferate in the gut and form a stable association. This is beneficial to the bacteria since they can be constantly spread by the flies as they move around. On the other hand, this is a form of farming as the next generation of flies benefit from the association with these particular bacteria during development. They become adults faster and are more fertile than if they develop with other bacteria encountered in nature. These advantages are also observed when flies develop in figs, a natural food source. Our findings show that D. melanogaster has stable colonizing bacteria in the gut and establish a new framework to study host-gut bacteria interactions.

microbiology↗