Microbiota of Galapagos iguanas and Aeolian sea turtles

To preserve environment and biodiversity is a major challenge of modern science. In the strategy of conservation, based on the implementation of basic knowledge, the identification of the intestinal microbiota of wild organisms (i.e. land iguanas from the Galapagos Islands and turtles from the Aeolian Islands) can be used as both basic knowledge and application tool.The quantitative and qualitative definition of microorganisms inhabiting the digestive tract of these reptiles, can provide an overview of great interest and it is still largely unexplored, while the comparison of the intestinal microbiota from urbanized and wild areas, can be another way to assess the impact of human presence.

The transfer of antibiotic resistance is a marker to follow the exchange of microorganisms between the man-impacted and natural compartments. The analysis of the incidence and nature of the genetic determinants of antibiotic resistance that occur naturally and/or are acquired by enteric bacteria of the intestinal microbiota, is an additional tool for evaluating the human impact by comparing the results found in animals from urbanized areas or intact ones.The work was started on land iguanas from the Galapagos Archipelago, a particularly interesting case because some islands are not exposed to human impact and so we can have some indication of the wildlife in the absence of disturbances, while others are subject to human impact (indigenous and/or tourists). From this system it is possible to get information on both the changes that already took place and on those in progress: a sort of "experiment-control" structure. The project included both the identification of the main components of the microbiota associated with the cloaca of land and marine iguanas, both the incidence and nature of resistance determinants.

The same work is now in progress on land iguanas from the French Antilles, in the Caribbean Sea.

The same aim and experimental approach has been applied to the study of the incidence and nature of resistance determinants in the intestinal microbiota of sea turtles (Caretta caretta L.) sampled in the Filicudi Island area, Aeolian Archipelago. In this case, healthy turtles were compared to others suffering feeding problems due to ingested hooks or plastic bags. Furthermore, on these sea turtles a pilot study was launched aimed both to evaluate the structure and composition of the entirety of carapace colonizers and to set up a unitary protocol for this type of study: both the macro-colonizers (epiphytic macroalgae, crustaceans, etc.) and the micro-colonizers (i.e. bacterial community) were analysed. Bacterial colonizers were analysed by using NGS (Next Generation Sequencing).

This work was possible thanks to the collaborations with: Gabriele Gentile, Department of Biology, Tor Vergata University, for iguanas; Monica Blasi, Filicudi Wildlife Conservation Association, Filicudi (Messina), Daniela Mattei of the National Health Institute in Rome, and Valeria Alduina, Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, University of Palermo, for the sea ​​turtles.


Blasi M., Rotini A., Bacci T., Targusi M., Bonanno Ferraro G., Vecchioni L., Alduina R., Migliore L. (2021) - NEW INSIGHTS INTO THE EPIBIONTS OF THE MEDITERRANEAN LOGGERHEAD SEA TURTLES. Biodiversity and Conservation, submitted.


Blasi M.F., Migliore L., Mattei D., Rotini A., Thaller M.C., Alduina R. (2020) - ANTIBIOTIC RESISTANCE OF GRAM-NEGATIVE BACTERIA FROM WILD CAPTURED LOGGERHEAD SEA TURTLES. Antibiotics, 9: 162. DOI: 10.3390/antibiotics9040162

Sea turtles have been proposed as health indicators of marine habitats and carriers of antibiotic-resistant bacterial strains, for their longevity and migratory lifestyle. Up to now, a few studies evaluated the antibacterial resistant flora of Mediterranean loggerhead sea turtles (Caretta caretta) and most of them were carried out on stranded or recovered animals. In this study, the isolation and the antibiotic resistance profile of 90 Gram negative bacteria from cloacal swabs of 33 Mediterranean wild captured loggerhead sea turtles are described. Among sea turtles found in their foraging sites, 23 were in good health and 10 needed recovery for different health problems (hereafter named weak). Isolated cloacal bacteria belonged mainly to Enterobacteriaceae (59%), Shewanellaceae (31%) and Vibrionaceae families (5%). Although slight differences in the bacterial composition, healthy and weak sea turtles shared antibiotic-resistant strains. In total, 74 strains were endowed with one or multi resistance (up to five different drugs) phenotypes, mainly towards ampicillin (~70%) or sulfamethoxazole/trimethoprim (more than 30%). Hence, our results confirmed the presence of antibiotic-resistant strains also in healthy marine animals and the role of the loggerhead sea turtles in spreading antibiotic-resistant bacteria.


Thaller M.C., Migliore L., Marquez C., Tapia W., Cedeño V., Rossolini G.M., Gentile G. (2010). TRACKING ACQUIRED ANTIBIOTIC RESISTANCE IN COMMENSAL BACTERIA OF GALÁPAGOS LAND IGUANAS: NO MAN, NO RESISTANCE. PLoS One, 5(2): e8989. DOI: 10.1371/journal.pone.0008989

Background: Antibiotic resistance, evolving and spreading among bacterial pathogens, poses a serious threat to human health. Antibiotic use for clinical, veterinary and agricultural practices provides the major selective pressure for emergence and persistence of acquired resistance determinants. However, resistance has also been found in the absence of antibiotic exposure, such as in bacteria from wildlife, raising a question about the mechanisms of emergence and persistence of resistant strains under similar conditions, and the implications for resistance control strategies. Since previous studies yielded some contrasting results, possibly due to differences in the ecological landscapes of the studied wildlife, we further investigated this issue in wildlife from a remote setting of the Galapagos archipelago.
Methodology/Principal Findings: Screening for acquired antibiotic resistance was carried out in commensal enterobacteria from Conolophus pallidus, the terrestrial iguana of Isla Santa Fe, where: i) the abiotic conditions ensure to microbes good survival possibilities in the environment; ii) the animal density and their habits favour microbial circulation between individuals; and iii) there is no history of antibiotic exposure and the impact of humans and introduced animal species is minimal except for restricted areas. Results revealed that acquired antibiotic resistance traits were exceedingly rare among bacteria, occurring only as non-dominant strains from an area of minor human impact.
Conclusions/Significance: Where both the exposure to antibiotics and the anthropic pressure are minimal, acquired antibiotic resistance traits are not normally found in bacteria from wildlife, even if the ecological landscape is highly favourable to bacterial circulation among animals. Monitoring antibiotic resistance in wildlife from remote areas could also be a useful tool to evaluate the impact of anthropic pressure.
iguana-cart1 iguana-cart2
Thaller M.C., Ciambotta M., Sapochetti M., Migliore L., Tapia W., Cedeño V., Gentile G. (2010). UNEVEN FREQUENCY OF Vibrio alginolyticus-GROUP ISOLATES AMONG DIFFERENT POPULATIONS OF GALÁPAGOS MARINE IGUANA (Amblyrhynchus cristatus). Environmental Microbiology Reports, 2(1): 179-184. DOI:  10.1111/j.1758-2229.2009.00132.x
The presence of Vibrio isolates was investigated in cloacal swabs from the Galápagos marine iguana (Amblyrhyncus cristatus). Such unique iguana is endemic to the Galápagos Archipelago, it is listed as vulnerable in the IUCN Red List (2009), and is strictly protected by CITES and Ecuador laws. Our results revealed an uneven isolation frequency of vibrios from animals living in different settings: maximal among the Santa Fe population, scarce at Bahía Tortuga but practically absent in the samples from Puerto Ayora and Plaza Sur. A 16S sequencing confirmed that the isolates belonged to the genus Vibrio, placing them within the V. alginolyticus group; the biochemical identification was, indeed, consistent with V. alginolyticus features. The reason of the observed discrepancy is not clear, but could be either linked to an higher pollution in the inhabited or more touristic places or to differential influence of chemical and physical parameters at a local scale. As V. alginolyticus is an opportunistic pathogen for man and it is known to cause disease in sea-living animals, the ability of these vibrios to enter and persist to a certain extent in the marine iguana gut should be regarded as a risk for health of both the animals and the human personnel involved in monitoring activities.

Luciana mostra l’iguana rosa (Conolophus marthae), n. 100, vulcano Wolf, Galapagos, giugno 2009.