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Background: High-altitude ecosystems are extreme environments that generate specific physiological, morphological, and behavioral adaptations in ectotherms. The shifts in gut microbiota of the ectothermic hosts as an adaptation to environmental changes are still largely unknown. We investigated the food ingested and the bacterial, fungal, and protistan communities in feces of the lizard Sceloporus grammicus inhabiting an altitudinal range using metabarcoding approaches. Results: The bacterial phyla Bacteroidetes and Firmicutes, and the genera Bacteroides and Parabacteroides dominated the core fecal bacteriome, while Zygomycota and Ascomycota, and the species Basidiobolus ranarum and Basidiobolus magnus dominated the core fecal mycobiome. The diet of S. grammicus included 29 invertebrate families belonging to Arachnida, Chilopoda, and Insecta. The diversity and abundance of its diet decreased sharply at high altitudes, while the abundance of plant material and Agaricomycetes was significantly higher at the highest site. The composition of the fecal microbiota of S. grammicus was different at the three altitudes, but not between females and males. Dietary restriction in S. grammicus at 4150 m might explain the high fecal abundance of Akkermansia and Oscillopira, bacteria characteristic of long fasting periods, while low temperature favored B. magnus. A high proportion of bacterial functions were digestive in S. grammicus at 2600 and 3100, while metabolism of aminoacids, vitamins, and key intermediates of metabolic pathways were higher at 4150 m. Different assemblages of fungal species in the lizard reflect differences in the environments at different elevations. Pathogens were more prevalent at high elevations than at the low ones. Conclusions: Limiting food resources at high elevations might oblige S. grammicus to exploit other food resources and its intestinal microbiota have degradative and detoxifying capacities. Sceloporus grammicus might have acquired B. ranarum from the insects infected by the fungus, but its commensal relationship might be established by the quitinolytic capacities of B. ranarum. The mycobiome participate mainly in digestive and degradative functions while the bacteriome in digestive and metabolic functions.

Wells used for drinking water often have a large biomass and a high bacterial diversity. Current technologies are not always able to reduce the bacterial population, and the threat of pathogen proliferation in drinking water sources is omnipresent. The environmental conditions that shape the microbial communities in drinking water sources have to be elucidated, so that pathogen proliferation can be foreseen. In this work, the bacterial community in nine water wells of a groundwater aquifer in Northern Mexico were characterized and correlated to environmental characteristics that might control them. Although a large variation was observed between the water samples, temperature and iron concentration were the characteristics that affected the bacterial community structure and composition in groundwater wells. Small increases in the concentration of iron in water modified the bacterial communities and promoted the growth of the iron-oxidizing bacteria Acidovorax. The abundance of the genera Flavobacterium and Duganella was correlated positively with temperature and the Acidobacteria Gp4 and Gp1, and the genus Acidovorax with iron concentrations in the well water. Large percentages of Flavobacterium and Pseudomonas bacteria were found, and this is of special concern as bacteria belonging to both genera are often biofilm developers, where pathogens survival increases.

In this study, the effect of deforestation and cultivation of maize (Zea mays L.) on the physicochemical characteristics and the bacterial community structure in soil were studied at the national park Área de Protección de Flora y Fauna Nevado de Toluca in Mexico. Soil was sampled from three forested areas in the national park, from three deforested areas grazed by animals and from three areas cultivated with maize. The soil was characterized chemically and biologically, whilst the bacterial community structure was investigated through 454 pyrosequencing of the 16S rRNA gene. The pH in the forest soil decreased from 6·1 to 5·3 in the maize-cultivated soil, whilst the soil organic C content decreased 1·4 times in the arable soil compared with the forest soil. The microbial biomass C decreased 2·9 times in the arable soil compared with the forest soil, but the metabolic quotient qCO 2 (ratio basal respiration to microbial biomass C) nearly doubled. Deforestation and maize cultivation reduced the abundance of Proteobacteria, Actinobacteria and Bacteroidetes, whereas Acidobacteria, Chloroflexi, Gemmatimonadetes and Firmicutes were resistant to these changes. It was found that soil characteristics were affected negatively by deforestation and nearly half of the organic matter was lost, and on these sloped fields, erosion will be high, further decreasing soil fertility. Although the relative abundance of a number of bacterial groups was reduced by deforestation, others were not affected by land-use change.key words: bacterial community structure; metabolic quotient qCO 2 ; microbial biomass C and N; soil organic matter; resistance of the bacterial community to land-use change

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