Gut Bacterial Communities Vary across Habitats and Their Diversity Increases with Increasing Glucocorticoids in Toad Tadpoles

Abstract

The gut microbiome is important for host health and can be influenced by environmental and hormonal changes. We studied the interactions between anthropogenic land use, glucocorticoid hormones, and gut bacterial communities in common toads (Bufo bufo). We sampled tadpoles from ponds of three habitat types (natural, agricultural, and urban ponds), examined gut microbiome composition using amplicon sequencing of the 16S rRNA gene, and measured the associated stress physiology using water-borne hormones. Tadpoles from different habitat types significantly differed in bacterial composition. However, bacterial richness, Shannon diversity, and Firmicutes to Bacteroidota ratio did not vary with habitat type. In contrast with other studies, we found a positive correlation between baseline corticosterone release rate and bacterial diversity. Stress response and negative feedback were not significantly correlated with bacterial diversity. These results suggest that, despite alterations in the composition of intestinal bacterial communities due to land-use change, common toad tadpoles in anthropogenic habitats may maintain their physiological health in terms of the “gut-brain axis”.

Linking microbiome and stress hormone responses in wild tropical treefrogs across continuous and fragmented forests

“…The relationship between glucocorticoids and the microbiome has received relatively little research attention, but some studies have reported general reductions in host-associated microbial diversity with increased glucocorticoid levels 2 – 4 , 89 – 91 . However, other studies report higher microbial diversity 1 or increases in potential opportunistic pathogenic taxa with increasing glucocorticoid levels 4 , 90 . Interestingly, two studies report that cortisol levels were negatively correlated with abundance of potentially probiotic lactic acid bacteria 4 , 89 .…”

“…nvironmental stressors negatively impact wildlife through many different mechanisms. One such mechanism includes synergistic interactions between stress responses and immune function, which can influence host fitness and disease susceptibility under environmental stress [1][2][3][4] . Amphibians are particularly susceptible to environmental stressors, are among the most threatened taxa globally 5 , and have suffered major declines in recent years due to habitat loss and disease [6][7][8][9][10] .…”

Exposure to Roundup and Antibiotics Alters Gut Microbial Communities, Growth, and Behavior in Rana berlandieri Tadpoles

“…We performed total DNA extraction for 16S rRNA gene amplicon. We analyzed samples following Gontang et al [ 56 ] and Gabor et al [ 57 ] for gut microbiome analysis. In summary, we extracted DNA from the samples by using Pure Link™ Microbiome DNA Purification Kit.…”

The gut microbiota-immune-brain axis in a wild vertebrate: dynamic interactions and health impacts

“…Studies in birds associated exploratory behaviour with microbiota diversity, while learning and memory performance have been correlated with compositional differences (Florkowski and Yorzinski, 2023;Slevin et al, 2020). The gut microbiota's links to stress have also been explored: in common toad tadpoles (Bufo bufo), elevated baseline corticosterone associates with higher microbial diversity (Gabor et al, 2022), while American red squirrels (Tamiasciurus hudsonicus)…”