Frogs Respond to Commercial Formulations of the Biopesticide Bacillus thuringiensis var. israelensis, Especially Their Intestine Microbiota

Abstract

It is generally believed that Bacillus thuringiensis var. israelensis (Bti) biopesticides are harmless to non-target organisms; however, new research shows controversial results. We exposed acutely and chronicallyLithobates sylvaticusandAnaxyrus americanus tadpoles until metamorphic climax to VectoBac 200G (granules) and VectoBac 1200L (aqueous suspension) at 300–20,000 ITU/L covering field-relevant concentrations and higher. The data show that the exposure parameters tested did not affect significantly the survival, total length, total weight, hepatosomatic index, gonadosomatic index, the expression of genes of interest (i.e., related to xenobiotic exposure, oxidative stress, and metamorphosis), and the intestine tissue layer detachment ofL. sylvaticusandA. americanus in a concentration–response pattern. In contrast, VectoBac 200G significantly increased the median time to metamorphosis ofL. sylvaticus tadpoles by up to 3.5 days and decreased the median by up to 1 day inA. americanus. VectoBac 1200L significantly increased the median time to metamorphosis ofL. sylvaticusandA. americanustadpoles by up to 4.5 days. Also, the exposure to VectoBac 200G and 1200L altered the intestine bacterial community composition inA. americanus at application rates recommended by the manufacturer, which led to an increase in the relative abundance of Verrucomicrobia, Firmicutes, Bacteroidetes, and Actinobacteria. Changes in the intestine microbiota might impact the fitness of individuals, including the susceptibility to parasitic infections. Our results indicate that the effect of Bti commercial products is limited; however, we recommend that Bti-spraying activities in amphibian-rich ecosystems should be kept minimal until there is more conclusive research to assess if the changes in the time to metamorphosis and microbiota can lead to negative outcomes in amphibian populations and, eventually, the functioning of ecosystems.

Urbanization increases stochasticity and reduces the ecological stability of microbial communities in amphibian hosts

“…Microbial DNA was extracted using the MN NucleoSpin 96 Soil kit (MACHEREY-NAGEL) according to the manufacturer’s instructions. The V3-V4 regions of the 16S rRNA gene were amplified using the universal primer pair 338F/341F and 806R/805R ( Yao et al, 2019 ; Gutierrez-Villagomez et al, 2021 ). Briefly, PCR thermocycling was carried out under the following conditions: 95°C for 5 min, followed by 30 cycles at 95°C for 30 s, 50°C for 30 s, 72°C for 60 s and a final extension at 72°C for 5 min.…”

The Taxonomic Status of Physalaemus cuqui Lobo, 1993, with the Description of a New Species of Physalaemus (Anura: Leptodactylidae) from Argentina and Paraguay

“…5, their supplementary data S1–S7); González et al (2021: 4, 15, their Figs. 2 and 6); Grenat et al (2021: 156); Gutierrez-Villagomez et al (2021: 12508); Marangoni and López (2021: 116); Müller et al (2021: 972); Peltzer et al (2021: 257, their Figs. 4 8…”

Community series in the wildlife gut microbiome and its implication for conservation biology, volume II

“…Microbial DNA was extracted using the MN NucleoSpin 96 Soil kit (MACHEREY-NAGEL) according to the manufacturer's instructions. The V3-V4 regions of the 16S rRNA gene were amplified using the universal primer pair 338F/341F and 806R/805R Gutierrez-Villagomez et al, 2021). Briefly, PCR thermocycling was carried out under the following conditions: 95°C for 5 min, followed by 30 cycles at 95°C for 30 s, 50°C for 30 s, 72°C for 60 s and a final extension at 72°C for 5 min.…”