Corrigendum: Composition and Diversity of CRISPR-Cas13a Systems in the Genus Leptotrichia.

[This corrects the article DOI: 10.3389/fmicb.2019.02838.].

Composition and Diversity of CRISPR-Cas13a Systems in the Genus Leptotrichia.

Clustered regularly interspaced short palindromic repeats (CRISPR)-Cas13a, previously known as CRISPR-C2c2, is the most recently identified RNA-guided RNA-targeting CRISPR-Cas system that has the unique characteristics of both targeted and collateral single-stranded RNA (ssRNA) cleavage activities. This system was first identified in Leptotrichia shahii. Here, the complete whole genome sequences of 11 Leptotrichia strains were determined and compared with 18 publicly available Leptotrichia genomes in regard to the composition, occurrence and diversity of the CRISPR-Cas13a, and other CRISPR-Cas systems. Various types of CRISPR-Cas systems were found to be unevenly distributed among the Leptotrichia genomes, including types I-B (10/29, 34.4%), II-C (1/29, 2.6%), III-A (6/29, 15.4%), III-D (6/29, 15.4%), III-like (3/29, 7.7%), and VI-A (11/29, 37.9%), while 8 strains (20.5%) had no CRISPR-Cas system at all. The Cas13a effectors were found to be highly divergent with amino acid sequence similarities ranging from 61% to 90% to that of L. shahii, but their collateral ssRNA cleavage activities leading to impediment of bacterial growth were conserved. CRISPR-Cas spacers represent a sequential achievement of former intruder encounters, and the retained spacers reflect the evolutionary phylogeny or relatedness of strains. Analysis of spacer contents and numbers among Leptotrichia species showed considerable diversity with only 4.4% of spacers (40/889) were shared by two strains. The organization and distribution of CRISPR-Cas systems (type I-VI) encoded by all registered Leptotrichia species revealed that effector or spacer sequences of the CRISPR-Cas systems were very divergent, and the prevalence of types I, III, and VI was almost equal. There was only one strain carrying type II, while none carried type IV or V. These results provide new insights into the characteristics and divergences of CRISPR-Cas systems among Leptotrichia species.

Correlations between drug resistance of Beijing/W lineage clinical isolates of Mycobacterium tuberculosis and sublineages: a 2009-2013 prospective study in Xinjiang province, China.

BACKGROUND: The prevalence of drug-resistant tuberculosis (TB) in Xinjiang is higher than in other regions of China, and Beijing/W lineage Mycobacterium tuberculosis (MTB) is the dominant strain of MTB in Xinjiang. However, information on multidrug-resistant (MDR) and extensively drug-resistant (XDR) TB, particularly the correlation between MDR and the Beijing/W lineage and the correlation between drug resistance and the Beijing/W sublineage strains, is limited. MATERIAL/METHODS: We conducted a prospective study to describe the prevalence of MDR/XDR TB, Beijing/W lineage and sublineage strains in Xinjiang in China from 2009 to 2013. All MTB underwent drug susceptibility testing to the first- and second-line anti-tuberculosis drugs. The Beijing/W lineages and sublineages were detected by large-sequence polymorphisms with polymerase chain reaction. RESULTS: A total of 410 clinical isolates were identified. The overall percentage of MDR and XDR cases in Xinjiang was 13.2% (54/410) and 13.0% (7/54), respectively. Overall, 9.8% (14/143) of the Beijing lineage MTB were MDR patients, and 15.6% (40/257) of the Non-Beijing lineage MTB were MDR patients. In the 143 Beijing MTB lineages, 11.2% isolates were in sublineage 105, 15.4% isolates were in sublineage 207, 69.2% isolates were in sublineage 181, and 4.2% isolates were in sublineage 150. None of the isolates were detected in sublineage 142. Significant differences between the Beijing/W and non-Beijing/W strains were observed regarding INH and EMB resistance, respectively. CONCLUSIONS: The prevalence of the MDR TB in Xinjiang remains high and imposes challenges for TB control. Four Beijing/W sublineage isolates were observed in Xinjiang. There was no correlation between MDR and the Beijing/W lineage and no correlation between drug resistance and the Beijing/W sublineage strains. Surveillance of the clinical isolates of MTB is recommended to strengthen the identification of MDR/XDR TB and sublineages of the Beijing/W strains.

An improved quantitative method for evaluation of ischemic injury and neuroprotection in mouse brain slices / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To establish a simpler and more accurate method for evaluating in vitro ischemic injury and neuroprotective effects of drugs through improving experimental instrument and quantitative index in mouse brain slices.</p><p><b>METHODS</b>An incubation instrument was developed and its application tested. 2,3,5-triphenyltetrazolium chloride (TTC) was used as a substrate to biosynthesize formazan standard in mouse brain slices, and formazan was isolated, purified and identified. Ischemic injury of mouse brain slices was induced by oxygen/glucose deprivation (OGD), the produced formazan from TTC in the cortex and striatum was measured at 490 nm spectrophotometrically. Edaravone and ONO-1078 were added into the incubation medium to observe their neuroprotective effects.</p><p><b>RESULT</b>The incubation instrument worked well for incubating brain slices and obtaining stable results efficiently. Standard formazan was biosynthesized and purified with a purity of 99.3%, and showed a linear range of 0.05 - 1 mg/ml in absorbance at 490 nm (r=0.9997). OGD decreased formazan production in the cortex and striatum in a duration-dependent manner. Edaravone (0.01 to 1 micromol/L) recovered OGD-induced decrease of formazan production, but ONO-1078 showed no effect.</p><p><b>CONCLUSION</b>The incubation instrument and quantitative measurement of formazan developed in this study are efficient,accurate and simple for evaluating ischemic injury and neuroprotection,which can be used in screening of neuroprotective drugs in vitro.</p>