ARTICLE | doi:10.20944/preprints201912.0354.v1
Subject: Biology And Life Sciences, Immunology And Microbiology Keywords: Lactobacillus helveticus; probiotics; whole genome sequencing; PacBio; probiotic genes; bacteriocins; gene expression
Online: 26 December 2019 (10:56:44 CET)
Whole-genome DNA sequencing of Lactobacillus D75 and D76 strains (Vitaflor, Russia) was performed using the PacBio RS II platform, followed by de novo assembly with SMRT Portal 2.3.0. The average nucleotide identity (ANI) test showed that both strains belong to the Lactobacillus helveticus, but not the L. acidophilus as previously assumed. 31 exopolysaccharide (EPS) production genes (nine of which form a single genetic cluster), 13 adhesion genes, 38 milk protein and 11 milk sugar utilization genes, 13 genes for and against specific antagonistic activity, aight antibiotic resistance genes, and also three CRISPR blocks and eight Cas I-B system genes were identified in the genomes of the both strains. The expression of some genes was confirmed. In fact, the presence of identified genes suggests that L. helveticus D75 and D76 are able to form biofilms on the outer mucin layer, inhibit the growth of pathogens and pathobionts, utilize milk substrates with the formation of digestible milk sugars and bioactive peptides, resist bacteriophages and show some genome-determined resistance to antibiotics, stimulate the host’s immune system. Pathogenicity genes have not been identified. The study results confirm the safety and high probiotic potential of the strains.
REVIEW | doi:10.20944/preprints202010.0281.v1
Subject: Biology And Life Sciences, Anatomy And Physiology Keywords: denitrification; evolution; thermophile; horizontal gene transfer; nitrate respiration; PacBio sequencing
Online: 13 October 2020 (14:00:29 CEST)
Genes coding for enzymes of the denitrification pathway appear randomly distributed among isolates of the ancestral genus Thermus, but only in few strains of the species T. thermophilus the pathway has been studied to a certain detail. Here, we review the enzymes involved in this pathway present in T. thermophilus NAR1, a strain extensively employed as a model for nitrate respiration, on the light of its full sequence recently assembled through a combination of PacBio and Illumina technologies in order to counteract the systematic errors introduced by the former technique. The genome of this strain is divided in four replicons, a chromosome of 2,021,843 pb, two megaplasmids of 370,865 and 77,135 bp and a small plasmid of 9,799 pb. Nitrate respiration is encoded in the largest megaplasmid, pTTHNP4, within a region that includes operons for O2 and nitrate sensory systems, a nitrate reductase, nitrate and nitrite transporters and a nitrate specific NADH dehydrogenase, in addition to multiple insertion sequences (IS), suggesting its mobility-prone nature. Despite nitrite is the final product of nitrate respiration in this strain, the megaplasmid encodes two putative nitrite reductases of the cd1 and Cu-containing types, apparently inactivated by IS. No nitric oxide reductase genes have been found within this region, although the NorR sensory gene, needed for its expression, is found near the inactive nitrite respiration system. These data clearly support that partial denitrification in this strain is the consequence of recent deletions and IS insertions in genes involved in nitrite respiration. Based on these data, the capability of this strain to transfer or acquire denitrification clusters by horizontal gene transfer is discussed.
ARTICLE | doi:10.20944/preprints202107.0562.v1
Subject: Biology And Life Sciences, Biochemistry And Molecular Biology Keywords: genome; transcriptome; gene models; Leishmania; Illumina sequencing; PacBio sequencing; expression levels; untranslated regions (UTRs); SL-additions sites; polyadenylation sites
Online: 26 July 2021 (10:23:40 CEST)
Leishmania major is the main causative agent of cutaneous leishmaniasis in humans. The Friedlin strain of this species (LmjF) was chosen when a multi-laboratory consortium undertook the objective of deciphering the first genome sequence for a parasite of the genus Leishmania. The objective was successfully attained in 2005, and this represented a milestone for Leishmania molecular biology studies around the world. Although the LmjF genome sequence was done following a shotgun strategy and using classical Sanger sequencing, the results were excellent and this genome assembly served as the reference for subsequent genome assemblies in other Leishmania species. Here, we present a new assembly for the genome of this strain (named LMJFC for clarity), generated by the combination of two high throughput sequencing platforms, Illumina short-read sequencing and PacBio Single Molecular Real-Time (SMRT) sequencing, which provides long-read sequences. Apart from resolving uncertain nucleotide positions, several genomic regions have been reorganized and a more precise composition of tandemly repeated gene loci was attained. Additionally, the genome annotation has been improved by adding 542 genes and more accurate coding-sequences defined for around two hundred genes, based on the transcriptome delimitation also carried out in this work. As a result, we are providing gene models (including untranslated regions and introns) for 11,238 genes. Genomic information ultimately determines the biology of every organism; therefore, our understanding of molecular mechanisms will depend on the availability of precise genome sequences and accurate gene annotations. In this regards, this work is providing an improved genome sequence and updated transcriptome annotations for the reference L. major Friedlin strain.