Toxin-antitoxin (TA) systems are growth-controlling genetic
elements consisting of an intracellular toxin protein and its
cognate antitoxin. TA systems have been spread among microbial
genomes through horizontal gene transfer and are
now prevalent in most bacterial and archaeal genomes. Under
normal growth conditions, antitoxins tightly counteract the
activity of the toxins. Upon stresses, antitoxins are inactivated,
releasing activated toxins, which induce growth arrest or cell
death. In this study, among nine functional TA modules in
Bosea sp. PAMC 26642 living in Arctic lichen, we investigated
the functionality of BoHigBA2. BohigBA2 is located close to
a genomic island and adjacent to flagellar gene clusters. The
expression of BohigB2 induced the inhibition of E. coli growth
at 37°C, which was more manifest at 18°C, and this growth
defect was reversed when BohigA2 was co-expressed, suggesting
that this BoHigBA2 module might be an active TA
module in Bosea sp. PAMC 26642. Live/dead staining and
viable count analyses revealed that the BoHigB2 toxin had
a bactericidal effect, causing cell death. Furthermore, we demonstrated
that BoHigB2 possessed mRNA-specific ribonuclease
activity on various mRNAs and cleaved only mRNAs
being translated, which might impede overall translation and
consequently lead to cell death. Our study provides the insight
to understand the cold adaptation of Bosea sp. PAMC 26642
living in the Arctic.
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Evaluating the Contribution of the Predicted Toxin–Antitoxin System HigBA to Persistence, Biofilm Formation, and Virulence in Burkholderia pseudomallei Itziar Chapartegui-González, Nittaya Khakhum, Jacob L. Stockton, Alfredo G. Torres, Igor E. Brodsky Infection and Immunity.2022;[Epub] CrossRef
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Transposon insertion site sequencing (TIS) is a technique that
determines the insertion profile of a transposon mutant library
by massive parallel sequencing of transposon-genomic
DNA junctions. Because the transposon insertion profile reflects
the abundance of each mutant in the library, it provides
information to assess the fitness contribution of each genetic
locus of a bacterial genome in a specific growth condition or
strain background. Although introduced only about a dozen
years ago, TIS has become an important tool in bacterial genetics
that provides clues to study biological functions and
regulatory mechanisms. Here, I describe a protocol for generating
high density transposon insertion mutant libraries
and preparing Illumina sequencing samples for mapping the
transposon junctions of the transposon mutant libraries using
Pseudomonas aeruginosa as an example.
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As the functions of probiotics within the same species may
not be shared, it is important to analyze the genetic characteristics
of strains to determine their safety and usefulness
before industrial applications. Hence the present study was
undertaken to determine functional genes, and beneficial activities
of strain LRCC5314, a bacterial strain isolated from
kimchi through comparative genomic analysis. Phylogenetic
analysis based on the 16S rRNA gene sequence showed that
strain LRCC5314 was a member of the species L. plantarum.
Whole genome size of strain LRCC5314 was sequence was
3.25 Mb long, with a G + C content of 44.5 mol% and 3,031
predicted genes. Strain LRCC5314 could metabolize hexoses
through homofermentation, which produces only lactic acid
from hexoses. According to gene annotation, strain LRCC-
5314 contained genes of EPS production and CRISPR. Moreover,
the strain contained genes that could encode a complete
biosynthetic pathway for the production of tryptophan, which
can be used as a precursor of serotonin. Notably, the tryptophan
and serotonin activities strain LRCC5314 were higher
than those of reference strains, L. plantarum ATCC 14917T,
DSM 20246, DSM 2601, and ATCC 8014, which reach tryptophan
amount of 0.784 ± 0.045 μM/ml in MRS broth and
serotonin concentration of 19.075 ± 0.295 ng/ml in HT-22
cells. These findings indicated that L. plantarum LRCC5314
could provide a source for serotonin production and could be
used as a functional probiotic for stress regulation.
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A 20-kDa ribonuclease (RNase) was purified from fresh fruiting bodies of cultured Schizophyllum commune mushrooms. The RNase was not adsorbed on Affi-gel blue gel but adsorbed on DEAE-cellulose and CM-cellulose. It exhibited maximal RNase activity at pH 6.0 and 70°C. It demonstrated the highest ribonucleolytic activity toward poly (U) (379.5 μ/mg), the second highest activity toward poly (C) (244.7 μ/mg), less activity toward poly (A) (167.4 μ/mg), and much weaker activity toward poly (G) (114.5 μ/mg). The RNase inhibited HIV-1 reverse transcriptase with an IC50 of 65 μM. No effect on [3H-methyl]-thymidine uptake by lymphoma MBL2 cells and leukemia L1210 cells was observed at 100 μM concentration of the RNase. A comparison of RNases from S. commune and Volvariella volvacea revealed that they demonstrated some similarities in N-terminal amino acid sequence, optimum pH and polyhomoribonucleotide specificity. However, some differences in chromatographic behavior and molecular mass were observed.
Legionella pneumophila, the cause of Legionnaires disease, is able to survive intracellularily in eukaryotic cells such as monocytes, macorphages, and protozoan ogranisms. During protein biosynthesis, the rph gene encodes ribonuclease (RNase) PH which functions as a phosphorolytic nuclease that removes nucleotides following the CCA terminus of tRNA and as a nucleotidyl-transferase which adds nucleotides to the ends of RNA molecules by usingnucelside diohosphates as substrates.In this sutdy, the rph gene was screened in pUC19 library employing a DNA probe whcich was constructed from PCR based on a consensus pattern of multiple alignment of RNas PH. The encoded protein consists of 235 amino acid residues with a calculated molecualr weight of 26,112 Daltons. The RNase PH signature domains are completely conserved.
The LRV1-4 capsid protein possesses an endoribonuclease activity that is responsible for the single sitespecific cleavage in the 5’ untranslated region (UTR) of its own viral RNA genome and the formation of a conserved stem-loop structure (stem-loop IV) in the UTR is essential for the accurate RNA cleavage by the capsid protein. To delineate the nucleotide sequences, which are essential for the correct formation of the stem-loop structure for the accurate RNA cleavage by the viral capsid protein, a wildtype minimal RNA transcript (RNA 5’ 249-342) and several synthetic RNA transcripts encoding pointmutations in the stem-loop region were generated in an in vitro transcription system, and used as substrates for the RNA cleavage assay and RNase mapping studies. When the RNA 5’ 249-342 transcript was subjected to RNase T1 and A mapping studies, the results showed that the predicted RNA secondary structure in the stem-loop region using FOLD analysis only existed in the presence of Mg2+ ions, suggesting that the metal ion stabilizes the stem-loop structure of the substrate RNA in solution. When point-mutated RNA substrates were used in the RNA cleavage assay and RNase T1 mapping study, the specific nucleotide sequences in the stem-loop region were not required for the accurate RNA cleavage by the viral capsid protein, but the formation of a stem-loop like structure in a region (nucleotides from 267 to 287) stabilized by Mg_2^+ ions was critical for the accurate RNA cleavage. The RNase T1 mapping and EMSA studies revealed that the Ca2+ and Mn2+ ions, among the reagents tested, could change the mobility of the substrate RNA 5’ 249-342 on a gel similarly to that of Mg_2^+ ions, but only Ca_2^+ ions identically showed the stabilizing effect of Mg_2^+ ions on the stem-loop structure, suggesting that binding of the metal ions (Mg_2^+ or Ca_2^+) onto the RNA substrate in solution causes change and stabilization of the RNA stem-loop structure, and only the substrate RNA with a rigid stem-loop structure in the essential region can be accurately cleaved by the LRV1-4 viral capsid protein.