Microbial community profile and water quality in a protected area of the caatinga biome

The Caatinga is a semi-arid biome in northeast Brazil. The Paraguaçú River is located in the Caatinga biome, and part of its course is protected by the National Park of Chapada Diamantina (PNCD). In this study we evaluated the effect of PNCD protection on the water quality and microbial community diversity of this river by analyzing water samples obtained from points located inside and outside the PNCD in both wet and dry seasons. Results of water quality analysis showed higher levels of silicate, ammonia, particulate organic carbon, and nitrite in samples from the unprotected area compared with those from protected areas. Pyrosequencing of the 16S rRNA genes revealed that Burkholderiales was abundant in samples from all three sites during both seasons and was represented primarily by the genus Polynucleobacter and members of the Comamonadaceae family (e.g., genus Limnohabitans). During the dry season, the unprotected area showed a higher abundance of Flavobacterium sp. and Arthrobacter sp., which are frequently associated with the presence and/or degradation of arsenic and pesticide compounds. In addition, genes that appear to be related to agricultural impacts on the environment, as well as those involved in arsenic and cadmium resistance, copper homeostasis, and propanediol utilization, were detected in the unprotected areas by metagenomic sequencing. Although PNCD protection improves water quality, agricultural activities around the park may affect water quality within the park and may account for the presence of bacteria capable of pesticide degradation and assimilation, evidencing possible anthropogenic impacts on the Caatinga

Muricauda brasiliensis sp. nov., isolated from a mat-forming cyanobacterial culture

Strain K001 was isolated from a cyanobacterial culture derived from Abrolhos, a reef bank microbial mat (South Atlantic Ocean—Brazil). Cells of K001 are Gram stain–negative, catalase and oxidase-positive, non-motile, rod-shaped, and with or without appendages. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain K001 belongs to the genus Muricauda. The highest strain K001 16S rRNA gene identity, ANI, and dDDH, respectively, are with M. aquimarina (98.90%, 79.23, 21.60%), M. ruestringensis (98.20%, 80.82, 23.40%), and M. lutimaris (97.86%, 79.23, 22.70%). The strain grows at 15–37 °C and between 0.5 and 10% NaCl. The major fatty acids of strain K001 are iso-C15:0, iso-C15:1 G, iso-C17:0 3-OH, and summed feature 3 (C16:1 ω6c and/or C16:1 ω7c). The polar lipids are represented by phosphatidylethanolamine, three unidentified aminolipids, and three unidentified polar lipids. The major respiratory quinone is MK-6. The G+C content of the DNA of strain K001 is 41.62 mol%. Based on polyphasic analysis of strain K001, it was identified as a novel representative of the genus Muricauda and was named Muricauda brasiliensis sp. nov. The type strain is K001 (=CBMAI 2315T = CBAS 752T)

Comparative analysis of pesticide-related genes in Paraguaçú River water samples obtained in the wet season.

<p>Samples were compared by ANOVA, followed by the Tukey–Kramer post hoc test (p < 0.05) without correction for multiple comparisons. Taxa with small effect sizes were removed by filtering (effect size = 8.00) using STAMP software.</p

General features of water samples obtained from sites on the Paraguaçú River.

<p>General features of water samples obtained from sites on the Paraguaçú River.</p

Principal component analysis (PCA) of the physicochemical parameters and bacterial community of Paraguaçú River water samples obtained from three sites (P1, unprotected area; P2 and P3, protected areas) during both wet and dry seasons.

<p>The ordination analysis was performed with ammonia, nitrite, nitrate, total nitrogen, orthophosphate, total phosphorous, silicate, dissolved organic carbon (DOC), particulate organic carbon (POC), and bacterial counts based on the correlation matrix.</p

Comparative analysis of pesticide-related genes in Paraguaçú River water samples obtained in the dry season.

<p>Samples were compared by ANOVA, followed by the Tukey–Kramer post hoc test (p < 0.05) without correction for multiple comparisons. Taxa with small effect sizes were removed by filtering (effect size = 8.00) using STAMP software.</p

Results of freshwater metagenomics studies.

<p>Results of freshwater metagenomics studies.</p

Study area.

<p>A) The area under National Park of Chapada Diamantina (PNCD) management is shown in green. The three sampling points on the Paraguaçú River are indicated on the map: P1, unprotected site outside the PNCD; P2 and P3, protected sites within the PNCD. The arrow indicates the direction of water flow. B) Unprotected sampling point P1. C) Protected sampling point P2. D) Protected sampling point P3.</p

Functional diversity of the Paraguaçú River’s metagenomes (P1, unprotected area; P2 and P3, protected area) in both wet and dry seasons. Classification was based on the SEED database level 1 in the MG-RAST server.

<p>A) Relative abundance of genes grouped by functional role. B) Comparative analysis of functional profiles of Paraguaçú River water samples obtained in the wet season. C) Comparative analysis of functional profiles of Paraguaçú River water samples obtained in the dry season. Samples were compared by t-test (p < 0.05), followed by the Bonferroni correction using STAMP software.</p