The Gut Bacterial Community of Mammals from Marine and Terrestrial Habitats

Abstract

After birth, mammals acquire a community of bacteria in their gastro-intestinal tract, which harvests energy and provides nutrients for the host. Comparative studies of numerous terrestrial mammal hosts have identified host phylogeny, diet and gut morphology as primary drivers of the gut bacterial community composition. To date, marine mammals have been excluded from these comparative studies, yet they represent distinct examples of evolutionary history, diet and lifestyle traits. To provide an updated understanding of the gut bacterial community of mammals, we compared bacterial 16S rRNA gene sequence data generated from faecal material of 151 marine and terrestrial mammal hosts. This included 42 hosts from a marine habitat. When compared to terrestrial mammals, marine mammals clustered separately and displayed a significantly greater average relative abundance of the phylum Fusobacteria. The marine carnivores (Antarctic and Arctic seals) and the marine herbivore (dugong) possessed significantly richer gut bacterial community than terrestrial carnivores and terrestrial herbivores, respectively. This suggests that evolutionary history and dietary items specific to the marine environment may have resulted in a gut bacterial community distinct to that identified in terrestrial mammals. Finally we hypothesize that reduced marine trophic webs, whereby marine carnivores (and herbivores) feed directly on lower trophic levels, may expose this group to high levels of secondary metabolites and influence gut microbial community richness.

Amphibian gut microbiota shifts differentially in community structure but converges on habitat-specific predicted functions

“…Food spectrum analysis from larvae stomach contents confirmed that larvae from these contrasting habitats ingest different food items. Diet is known to influence gut microbial communities in fish2123, humans19, other mammals205051 and amphibians2548. However, in many instances studies were unable to fully separate different dietary intake from host genetics (that is, host-specific factors within the gut environment)23 because different species were compared.…”

Colony Location and Captivity Influence the Gut Microbial Community Composition of the Australian Sea Lion (Neophoca cinerea)

“…For large-sized species, such as marine mammals, only a few animals are kept in captive facilities, presenting further sampling limitations in studies contrasting individuals from wild and captive sources. Here, our sample size of 33 wild and 10 captive animal samples from a single species was far greater than that of previous studies investigating the microbiota of marine mammals (5,17,19).…”

“…Comparisons of the compositions of gut microbiota of terrestrial and marine mammals have shown that the predominant phyla differ significantly between the two groups and that marine carnivores display richer microbial diversity than do terrestrial carnivores (17). However, marine mammal samples used for studies and comparisons of microbiota have almost entirely come from seals of various species (5,(17)(18)(19)(20)(21).…”

“…However, marine mammal samples used for studies and comparisons of microbiota have almost entirely come from seals of various species (5,(17)(18)(19)(20)(21). Such studies have found that the microbiota are largely dominated by four phyla, Firmic-utes, Bacteroidetes, Fusobacteria, and Proteobacteria, and, to a lesser extent, by Actinobacteria (5,(18)(19)(20)(21).…”

The life aquatic: advances in marine vertebrate genomics

“…Although there are still major gaps in our knowledge of how microorganisms interact with and affect marine vertebrates, recent studies on the microbiota from marine mammals have improved our understanding of the diversity of microorganisms found in larger marine species. Specifically, it has been shown that there are significant differences in bacterial communities in marine mammals compared with those found in terrestrial mammals 97,98 , which indicates that microorganisms may be important during the transition from land to sea and vice versa. Despite this land-versus-sea dichotomy, there are still significant differences in microbiota found in marine mammals, exemplified by the finding that dolphins and sea lions that have highly similar diets and that were caught in the same area (San Diego Bay, California, USA) harboured substantially different microbial communities 98 .…”