ABSTRACT
Aims: Phosphorus (P) is an essential element for life, finite and irreplaceable. Its constant exploration on a global scale has motivated frequent alerts regarding an eventual crisis due to the shortage of this nutrient. However, it is possible to recycle it and reintroduce it into the ecological cycle. One viable alternative is the microbial recovery of phosphate. Study design: This study is based on systematic bioprospection of bacteria in phosphate-deficient Amazon regions. Place and Duration of Study: Bacteria were isolated from black water samples, collected in the Rio Pretinho, located at Serra do Aracá, Barcelos, Amazonas, Brazil, from January to July 2019. Methodology: Microbial isolation was performed in Luria Bertani agar medium. For the genomic study, the isolate with the best performance in the phosphate uptake test was chosen. The WGS was carried out in a Illumina HiSeq 2500 System. The assembly of the draft genome was carried out with the SPAdes and the annotation by the NCBI Prokaryotic Genome Annotation Pipeline (PGAP). Results: Serratia nevei 9rpt1 recovers 90% of the phosphate available in the culture medium. Its draft genome comprises 5.4 MB, the GC content is 59.52% and 4,922 coding sequences were identified, among these, two pst operons: one complete, containing the five pst genes and one missing pstS, pstC and phoU genes. Conclusion: Serratia nevei 9rpt1, isolated from an Amazonian environment poor in phosphate, is very efficient to uptake this nutrient in a Pi starvation condition. The genomic findings revealed this strain has an additional high affinity Pi uptake pst system containing the ATP-binding protein PstB, the canonical permease PstA, a putative permease other than PstC, upstream of the PstA and two essential enzymes in the polyphosphate metabolism: polyphosphate kinase 1 and exopolyphosphatase.
ABSTRACT
50 root dentin sections were obtained from 25 extracted premolars and divided randomly into 5 groups of 10 samples each. Except group 1, all the other group specimens were demineralised by immersing in a demineralising solution for 96 hours at 370C. The specimens were then subjected to surface treatment with grape seed extract, silverdiamine fluoride and calcium sucrose orthophosphate complex according to the groups. The samples were stored in artificial saliva during the intervals and subjected to pH cycling and evaluated using SEM-EDAX and the results statistically compared. The tested remineralizing agents showed statistically significant increase in remineralization when compared to the demineralized group. Calcium sucrose orthophosphate showed the highest Ca/Pvalues followed by Silver diamine flouride and grape seed extract