Brumadinho dam collapse induces changes in the microbiome and the antibiotic resistance of the Paraopeba River (Minas Gerais, Brazil)

The rupture of the Córrego do Feijão dam in Brumadinho (January 25, 2019) caused serious damage to the Paraopeba River and compromised the quality of its waters for human consumption. However, the possible effects of the dam collapse on the river microbiome and its antibiotic resistance profiles are unknown. The present study aims to analyse the possible shifts in microbial diversity and enhancement of antibiotic resistance in the Paraopeba River. To this end, two sampling campaigns (February and May 2019) were performed to obtain water across the entire Paraopeba River (eight sampling locations: Moeda, Brumadinho, Igarapé, Juatuba, Varginha, Angueretá, Retiro Baixo and Três Marias; ~464 km). This sampling scheme enabled determining the effects of the disaster on the river microbiome. Total DNA and microbial isolation were performed with these water samples. The 16S rRNA-based microbiome analyses (n = 24; 2.05 million 16S rRNA reads) showed changes in microbial diversity immediately after the disaster with the presence of metal-indicating bacteria (Acinetobacter, Bacillus, Novosphingobium, and Sediminibacterium). Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) identification of bacterial isolates (n = 170) also disclosed possible indicators of faecal contamination across the Paraopeba (Cloacibacterium, Bacteroides, Feaecalibacterium, Bifidobacterium, Citrobacter, Enterobacter, Enterococcus and Escherichia). Antibiotic resistance increased significantly to ampicillin, ampicillin/sulbactam, amoxicillin/clavulanate, ceftriaxone, and cefalotin among isolates obtained in May after the disaster. The effects of toxic mud on microbiomes were felt at all points sampled up to Anguereta. The ore mud may have exacerbated the growth of different antibiotic-resistant, metal-resistant, and faecal-indicating bacteria in the Paraopeba River.

Severe impacts of the Brumadinho dam failure (Minas Gerais, Brazil) on the water quality of the Paraopeba River

On 25 January 2019, Córrego do Feijão's tailing dam at Brumadinho city (Minas Gerais, Brazil) breached, leaving over 250 people dead. At least 12 million cubic meters of ore tailing were spread into Paraopeba River and the surrounding area. To evaluate the short-term impacts of the Brumadinho dam rupture on the environment, we performed biogeochemical, microbiological and ecotoxicological analyses across 464 km of the Paraopeba River in the week following the disaster (1 February 2019) and four months latter (27-29 May 2019). Immediately after the disaster, the water turbidity was 3000 NTU, 30 times greater than the standard recommended by the Brazilian Resolution for Water Quality (CONAMA 357). Up to a 60-fold increase in iron tolerant microbial colony forming unities was observed up to 115 km downstream of the dam failure in May 2019 (compared with February 2019), suggesting changes in microbial metabolic profiles. In the second sampling (May 2019), the ecotoxicological analyses indicate higher zebrafish embryo mortality (up to ~85% embryo mortality) rates in Retiro Baixo (304 km from dam failure location). However, increased zebrafish mortality in Retiro Baixo and Três Marias reservoirs may not be related exclusively to the dam failure. The causal nexus of mortality may be associated with other factors (e.g. local sewage pollution). Our study suggests that independent monitoring programs are needed to quantify the extent of potential impacts caused by the anthropogenic use of the river and to promote the recovery of the impacted area.

Effects of supplementing methionine hydroxy analog on beef cow performance, milk production, reproduction, and preweaning calf performance

Mature Simmental × Angus cows (214 cows; 635 ± 7 kg) were utilized to determine the effects of late gestation and early postpartum supplementation of methionine hydroxy analog (MHA) on cow BW, BCS, milk production, milk composition, reproduction, and calf performance until weaning in a fall-calving, cool-season grazing system. Cows were stratified by BW, age, AI sire, and assigned to 1 of 12 pastures (17 or 18 cows·pasture). Pastures were randomly allotted to 1 of 2 treatments: control (0.45 kg·cow·d of wheat midd-based pellets, = 6) or supplement including MHA (0.45 kg·cow·d of wheat midd-based pellets including 10 g MHA supplied as MFP (Novus International, Inc., St. Charles, MO; = 6). Treatments were fed 23 ± 7 d prepartum through 73 ± 7 d postpartum. Cow BW was collected at postcalving (27 ± 7 d postpartum), end of supplementation (73 ± 7 d postpartum), AI, pregnancy check, and end of trial (192 and 193 ± 7 d postpartum). At 73 ± 7 d postpartum, a subset of cow-calf pairs was used in a weigh-suckle-weigh procedure to determine milk production, and milk samples were taken to determine milk composition ( = 45·treatment). Serum from blood was collected at 73 ± 7 and 83 ± 7 d postpartum to determine cow cyclicity and concentrations of 2-hydroxy4-(methylthio) butanoic acid (HMTBa) and L-Methionine. After supplementation, all cow-calf pairs were managed as a common group until weaning (193 ± 7 d of age). Cows were bred via AI at 97 ± 7 d postpartum and clean-up bulls were turned out 11 d post-AI for a 55-d breeding season. Cows fed MHA had greater ( < 0.01) serum concentrations of HMTBa. Cow BW and BCS were not different ( ≥ 0.10) at any time points between treatments. There was no treatment effect ( ≥ 0.17) on calf birth BW, calf weaning BW (193 ± 7 d of age), or calf ADG. Calculated 24-h milk production, milk composition and component production did not differ ( ≥ 0.21). There were no differences ( ≥ 0.50) in percentage of cows cycling, AI conception rate, and overall pregnancy rate between treatments. Post-trial nutritional modeling suggests cows experienced several nutritional deficiencies beyond methionine (Met) that limited the response to Met supplementation. Although supplementation of MHA during late gestation through estimated peak lactation increased serum HMTBa concentrations, it did not affect cow performance, cow milk production, or calf performance when fall-calving cows grazed cool-season forages.

Daily hemodialysis: a nursing perspective

Daily hemodialysis can be performed in the center or at home for varying lengths of time. Short daily hemodialysis (SDHD) can be defined as one and one half- to three-hour treatments performed 6 days per week. Nocturnal hemodialysis (NHD) is performed for 6 to 10 hours, 5 to 7 nights per week. Patient selection criteria can range from basic requirements, such as the ability to communicate, to medical necessity related to comorbid conditions. Central venous catheters (CVCs), mature arteriovenous fistulas, and synthetic grafts have been used successfully for daily dialysis therapies, although documented experience with grafts is somewhat limited. Documented nursing issues surrounding these therapies are very limited. Few changes are required to adapt daily dialysis to the in-center environment. Patient training strategies and scheduling for the home application vary between institutions, but the core approaches remain the same. Daily hemodialysis therapies can be integrated easily into existing home hemodialysis programs with very little extra effort. This article discusses nursing issues and provides relevant information for those who are interested in incorporating daily hemodialysis (DHD) therapies into their program.

Globin-coupled sensors: a class of heme-containing sensors in Archaea and Bacteria

The recently discovered prokaryotic signal transducer HemAT, which has been described in both Archaea and Bacteria, mediates aerotactic responses. The N-terminal regions of HemAT from the archaeon Halobacterium salinarum (HemAT-Hs) and from the Gram-positive bacterium Bacillus subtilis (HemAT-Bs) contain a myoglobin-like motif, display characteristic heme-protein absorption spectra, and bind oxygen reversibly. Recombinant HemAT-Hs and HemAT-Bs shorter than 195 and 176 residues, respectively, do not bind heme effectively. Sequence homology comparisons and three-dimensional modeling predict that His-123 is the proximal heme-binding residue in HemAT from both species. The work described here used site-specific mutagenesis and spectroscopy to confirm this prediction, thereby providing direct evidence for a functional domain of prokaryotic signal transducers that bind heme in a globin fold. We postulate that this domain is part of a globin-coupled sensor (GCS) motif that exists as a two-domain transducer having no similarity to the PER-ARNT-SIM (PAS)-domain superfamily transducers. Using the GCS motif, we have identified several two-domain sensors in a variety of prokaryotes. We have cloned, expressed, and purified two potential globin-coupled sensors and performed spectral analysis on them. Both bind heme and show myoglobin-like spectra. This observation suggests that the general function of GCS-type transducers is to bind diatomic oxygen and perhaps other gaseous ligands, and to transmit a conformational signal through a linked signaling domain.

Genome sequence of Halobacterium species NRC-1

We report the complete sequence of an extreme halophile, Halobacterium sp. NRC-1, harboring a dynamic 2,571,010-bp genome containing 91 insertion sequences representing 12 families and organized into a large chromosome and 2 related minichromosomes. The Halobacterium NRC-1 genome codes for 2,630 predicted proteins, 36% of which are unrelated to any previously reported. Analysis of the genome sequence shows the presence of pathways for uptake and utilization of amino acids, active sodium-proton antiporter and potassium uptake systems, sophisticated photosensory and signal transduction pathways, and DNA replication, transcription, and translation systems resembling more complex eukaryotic organisms. Whole proteome comparisons show the definite archaeal nature of this halophile with additional similarities to the Gram-positive Bacillus subtilis and other bacteria. The ease of culturing Halobacterium and the availability of methods for its genetic manipulation in the laboratory, including construction of gene knockouts and replacements, indicate this halophile can serve as an excellent model system among the archaea.

An archaeal aerotaxis transducer combines subunit I core structures of eukaryotic cytochrome c oxidase and eubacterial methyl-accepting chemotaxis proteins

Signal transduction in the archaeon Halobacterium salinarum is mediated by three distinct subfamilies of transducer proteins. Here we report the complete htrVIII gene sequence and present analysis of the encoded primary structure and its functional features. HtrVIII is a 642-amino-acid protein and belongs to halobacterial transducer subfamily B. At the N terminus, the protein contains six transmembrane segments that exhibit homology to the heme-binding sites of the eukaryotic cytochrome c oxidase. The C-terminal domain has high homology with the eubacterial methyl-accepting chemotaxis protein. The HtrVIII protein mediates aerotaxis: a strain with a deletion of the htrVIII gene loses aerotaxis, while an overproducing strain exhibits stronger aerotaxis. We also demonstrate that HtrVIII is a methyl-accepting protein and demethylates during the aerotaxis response.

Sensory rhodopsin II transducer HtrII is also responsible for serine chemotaxis in the archaeon Halobacterium salinarum

Previously, we demonstrated that the methyl-accepting protein HtrII is the transducer for photoreceptor sensory rhodopsin II. Here, we provide experimental evidence that HtrII is also a chemotransducer. Using an agarose-in-plug bridge method, we show that an HtrII overexpression strain has a quicker response to serine than does an HtrII deletion strain. Furthermore, an in vivo flow assay demonstrates that the deletion strain is unable to modulate methylesterase activity after serine addition or photostimulation, while the overexpression strain shows distinct methanol peaks following both types of stimuli.