Construction of EF-G knockdown strain of Mycobacterium smegmatis and drug resistance analysis / 生物工程学报

As the only translational factor that plays a critical role in two translational processes (elongation and ribosome regeneration), GTPase elongation factor G (EF-G) is a potential target for antimicrobial agents. Both Mycobacterium smegmatis and Mycobacterium tuberculosis have two EF-G homologous coding genes, MsmEFG1 (MSMEG_1400) and MsmEFG2 (MSMEG_6535), fusA1 (Rv0684) and fusA2 (Rv0120c), respectively. MsmEFG1 (MSMEG_1400) and fusA1 (Rv0684) were identified as essential genes for bacterial growth by gene mutation library and bioinformatic analysis. To investigate the biological function and characteristics of EF-G in mycobacterium, two induced EF-G knockdown strains (Msm-ΔEFG1(KD) and Msm-ΔEFG2(KD)) from Mycobacterium smegmatis were constructed by clustered regularly interspaced short palindromic repeats interference (CRISPRi) technique. EF-G2 knockdown had no effect on bacterial growth, while EF-G1 knockdown significantly retarded the growth of mycobacterium, weakened the film-forming ability, changed the colony morphology, and increased the length of mycobacterium. It was speculated that EF-G might be involved in the division of bacteria. Minimal inhibitory concentration assay showed that inhibition of EF-G1 expression enhanced the sensitivity of mycobacterium to rifampicin, isoniazid, erythromycin, fucidic acid, capreomycin and other antibacterial agents, suggesting that EF-G1 might be a potential target for screening anti-tuberculosis drugs in the future.

Synthesis, characterization, anti-mycobacterial activity and in silico study of new 2,5-disubstituted-1,3,4-oxadiazole derivatives

@#A series of new 2,5-disubstituted-1,3,4-oxadiazole derivatives (5a-j and 6a-j) have been designed and synthesized in four-steps. Sixteen compounds among the twenty compounds are reported for the first time. The compounds were characterized and confirmed by the FTIR, 1D- and 2D-NMR and HRMS analyses, and were tested against Mycobacterium smegmatis and Mycobacterium tuberculosis H37Ra. Compound 5d was the most active against M. smegmatis with MIC value of 25 µM, and exhibited cidal activity with MBC of 68 µM, respectively. The time-kill assay showed the good killing rate at 77% with the combination of isoniazid (INH). In addition, checkboard assay confirmed the interaction of compound 5d was categorised as additive. Docking simulation has been performed to position 5d into the pantothenate synthetase active site with binding free energy value –8.6 kcal mol-1. It also occupied the same active site as that of standard native ligand with similar interactions, which clearly indicate their potential as pantothenate synthetase inhibitor.

Immune responses in mice induced with a TSOL18 recombinant Mycobacterium smegmatis vaccine of Taenia solium / 中华地方病学杂志

Objective To observe humoral and cellular immune responses induced in mice by a TSOL18 recombinant Mycobacterium smegmatis (MS) vaccine of Taenia solium.Methods Sixty specific pathogen-free (SPF) Kunming mice (18-22 g,half male and half female) were divided into 3 groups by random number table method,20 mice in each group.One group was administered with recombinant MS-TSOL18 vaccine,one group was administered with MS as control,and one group was administered phosphate buffer saline (PBS) as control.Kunming mice were vaccinated once every two weeks for 2 times through intragastric administration.At 0,2,4,6,and 8 weeks after immunization,blood sample was collected and serum was separated.The levels of IgG and IgG2a in serum were detected using enzyme linked immunosorbent assay (ELISA).The spleen was separated to prepare spleen suspension.The proliferation of spleen lymphocyte with the stimulation of a specific antigen was detected by CCK-8.The levels of interleukin (IL)-2 and IL-4 in spleen cell culture supernatant with the stimulation of a specific antigen were detected by ELISA.Results Compared with MS control group (IgG:0.160 ± 0.019,0.187 ± 0.038,0.193 ± 0.050,0.170 ± 0.005;IgG2a:0.213 ± 0.010,0.198 ± 0.012) and PBS control group (IgG:0.159 ± 0.015,0.184 ± 0.029,0.191 ± 0.025,0.165 ± 0.018;IgG2a:0.198 ± 0.032,0.178 ± 0.025),the levels of specific IgG (0.310 ± 0.034,0.391 ± 0.029,0.443 ± 0.030,0.373 ± 0.021) in recombinant MS-TSOL18 vaccine group increased at 2,4,6,and 8 weeks after immunization (P ＜ 0.05),the levels of specific IgG2a (0.446 ± 0.056,0.339 ± 0.026) in recombinant MS-TSOL18 vaccine group increased at 6 and 8 weeks after immunization (P ＜ 0.05),and reached the highest level by the 6th week.After antigen stimulation,compared with MS and PBS control groups,the levels of spleen lymphocyte proliferation increased at 2,4,6,and 8 weeks after immunization (P ＜ 0.05),and reached the highest level by the 6th week.After antigen stimulation,compared with MS and PBS control groups,the levels of IL-2 and IL-4 in spleen lymphocyte culture supernatant increased at 2,4,6,and 8 weeks after immunization (P ＜ 0.05),and reached the highest level by the 6th and 4th weeks,respectively.Conclusion The recombinant MS-TSOL18 vaccine of Taenia solium might induce mice to produce humoral and cellular immune responses.

Virtual screening and preliminary validation of anti-tuberculosis components of traditional Chinese medicine / 国际中医中药杂志

Objective To verify a method of calculation and prediction by screening the antibacterial components of classical Chinese medicinal herbs (TCM) for anti tuberculosis, and preliminarily evaluate the anti tuberculosis effect of the selected components. Methods The components database of Stemona, Bletilla striata and Chuanbei was established. Dock method was used to predict the anti tuberculosis components from the database, and then mycobacterium smegmatis, MIC and inhibition zone methods were used to evaluate the anti-tuberculosis effect of these predicted components. Results Three ingredients were selected. In vitro experiments also showed that the selected ingredients had the effect of anti-mycobacterium smegmatis by MIC and inhibition zone . Conclusions The virtual screening method could decrease consumption and increase the efficiency of finding anti-tuberculosis ingredients of TCM.

Different characteristics between mycobacteriophage Chy1 and D29, which were classified as cluster A2 mycobacteriophages.

Purpose: The aim of this study was to isolate a novel mycobacteriophage and then explore its anti‑tuberculosis (TB) potential. Materials and Methods: Phage was isolated from enriched soil sample. A total of 36 mycobacterial strains obtained from clinical specimens were subjected to investigate the host range of phage by the spot lysis assay. Biological characteristics were investigated through growth curve, host range and phage antimicrobial activity in vitro. Then, genome sequencing and further analysis were accomplished by using an ABI3730XL DNA sequencer and comparative genome, respectively. Results: A lytic mycobacteriophage (Chy1) was isolated and the plaque morphology was similar to D29. The genome of Chy1 was estimated to be about 47,198 base pair (bp) and strong similarity (97.4% identity) to D29, especially, the Chy1 gene 7 encoding holin which is considered as a clock controlling growth cycle of the corresponding phage, was identical (100% identity) to phage D29 gene 11, thus classifying Chy1 as a member of the cluster A2 family. However, to our surprise, Chy1 can infect a narrower range of host‑mycobacterial strains than that of D29. The latent period of Chy1 was quite longer compared to D29. Moreover, Chy1 has a weaker ability to lyse Mycobacterium smegmatis compared to D29. Conclusions: The sequence of Chy1 showed 97.4% homology with the genome sequence of D29, but there was a large difference in their biological characteristics. Overall, the results of this investigation indicate that Chy1 is not an ideal candidate for developing mycobacteriophage‑based anti‑TB therapies but for future researches to investigate the reason why biological characteristics of Chy1 and D29 were remarkably different.

Effect of Methylene Blue-mediated Photodynamic Therapy on Wild-type and Ciprofloxacin-resistant Mycobacterium smegmatis

Tuberculosis (TB) patients are normally treated with a combination of antibiotics. However, with improper or incomplete treatment of antibiotics, the disease may progress to multidrug-resistant TB (MDR-TB). The treatment of MDR-TB is very costly and inefficient. Therefore, there is a great demand of new therapeutic approaches for MDR-TB such as photodynamic therapy. In this study, we tried to optimize the conditions for photodynamic inactivation of TB using methylene blue as a photosensitizer. Different combinations of methylene blue concentrations and light doses were tested for their photodynamic effects to A549 cells or Mycobacterium smegmatis (M. smegmatis). We also tested the effect of photodynamic therapy on ciprofloxacin-resistant M. smegmatis. Methylene blue treatment alone did not affect the survival rates of A549 cells or bacteria up to 5 µg/ml. When the A549 and M. smegmatis cells treated with methylene blue were irradiated with laser light (wavelength, 630 nm), photodynamic inactivation of cells was increased in methylene blue concentration- and light dose-dependent manners. Interestingly, the ciprofloxacin-resistant M. smegmatis exhibited higher level of susceptibility to methylene blue-mediated photodynamic inactivation. This study suggests that photodynamic therapy at 3.6 J/cm2 in the presence of 5 µg/ml methylene blue may be an appropriate range for therapy due to the high bactericidal activity against high level of ciprofloxacin-resistant M. smegmatis and the low damaging effect to mammalian cells. This study demonstrates that photodynamic therapy could be a potential alternative for MDR-TB treatment.

The Effect of Myeloid Differentiation Factor 88 Inhibitor ST2825 on the Autophagy of THP-1 Cells Infected with Recombinant Mycobacteriumsmegmatis / 中国医科大学学报

Objective To investigate the effect of myeloid differentiation factor 88 inhibitor ST2825 on the autophagy of THP?1 cells infected by re?combinant mycobacterium smegmatis. Methods The myeloid differentiation factor 88 inhibitor ST2825 was applied on the THP?1 cells infected by recombinant mycobacterium smegmatis,and three groups were defined:the test group with ST2825 treatment,the control group without ST2825 treatment,and the blank group. Autophagosomes were observed under the fluorescence microscope,and the mRNA expression of Beclin?1 gene and Bcl?2gene was analyzed by RT?PCR. Results Compared with the control group,the number of autophagy fluorescent dots in the test group was ob?viously reduced(P<0. 05),and the expression levels of Beclin 1 gene and Bcl?2 gene were declined as indicated by the RT?PCR detection. Con?clusion The myeloid differentiation factor 88 inhibitor ST2825 might inhibit the autophagy of THP?1 cells through interfering the separation of Be?clin?1 and Bcl?2.

Siderochelins with anti-mycobacterial activity from Amycolatopsis sp. LZ149 / 中国天然药物

Three new compounds, namely siderochelins D (2), E (3), and F (4), together with one known siderochelin A (1), were isolated from Amycolatopsis sp. LZ149 and elucidated by spectroscopic analyses including1D- and 2D-NMR and X-ray single crystal diffraction. Compounds 1-3 showed antibacterial activity against Mycobacterium smegmatis.

Recombinant Mycobacterium smegmatis expressing taco mRNA specific 10-23 deoxyribozyme mediate inhibition of taco expression in macrophage / 中华微生物学和免疫学杂志

Objective To construct a recombinant bacterial vaccine which can express specific 10-23 deoxyribozyme(DZ) in macrophage, identify the intracellular production of specific 10-23DZ and detect the activity of this recombinant bacterial vaccine on inhibiting the expression of TACO gene in macrophage.Methods The pSDE02 was obtained by inserting the replicon of Mycobacterium into pSDE01, a plasmid which can express 10-23DZ in eukaryotic cells. The expression sequence of DZ1, a 10-23DZ targeting the TACO mRNA of macrophage designed in our previous study was synthesized and inserted into pSDE02. The resulted plasmid was named pDZM01. pDZM01 was then transferred into Mycobacterium smegmatis by electroperation. The recombinant M. smegmatis, named rMs-DZ1 was screened on low-salt LB medium containing Zeocin and identified by Colony PCR. The targeted delivery property of recombinant M. smegmatis was observed by Ziehl-Heelson stain and GFP expression observation via fluorescence microscope. rMs-DZ1 was used to infect RAW264.7 cells and the expression of DZ1 in macrophage was identified by dot-blot assay. At 24 h and 48 h after infection, total RNA and proteins were extracted and the TACO mRNA and protein expression level was assayed by RT-PCR and western-blot respectively. Results Restrictive analysis and sequencing data showed that the Mycobacterium-eukaryotic cell shuttle plasmid pSDE02 and pDZM01 was successfully constructed. rMs-DZ1 was confirmed by colony PCR. When engulfed by macrophage, rMs-DZ1 would express DZ1 in RAW264.7 cells and inhibit the expression of taco gene. When compared to uninfected macrophage, rMs-DZ1 significantly reduced the taco mRNA by 67.90% and 57.14% and down-regulated the expression of TACO protein by 53.85% and 68.92% at 24 h and 48 h respectively. Conclusion A recombinant M. smegmatis vaccine was successfully constructed which could generate specific 10-23DZ in macrophage and inhibit the expression of target gene of interest. To our knowledge, this is the first bacterial vector which can express intracellularly 10-23DRz in targeted manner. This study may further prompt the feasibility of using 10-23 DNAzyme to achieve effective and targeted gene silence.

Enzymatic characterization of Mycobacterium smegmatis ADP-ribosyltransferase

ADP-ribosyltransferase (ADPRT) catalyzes the reaction in which the ADP-ribose moiety of beta-NAD+ is transferred to specific amino acid residues in target proteins. The ADPRT of Mycobacterium smegmatis has been known to inactivate rifampin through ADP-ribosylation. However, the enzymatic characteristics and functions of the enzyme have not been elucidated yet. In this study, the ADPRT-glutathione S-transferase (GST) fusion protein was expressed in Escherichia coli and enzymatic characteristics of the fusion protein were investigated. ADPRT-GST fusion protein was an ADPribosyltransferase that had no NAD glycohydrolase activity. ADPRT-GST fusion protein showed no self-inactivation phenomenon that is a universal nature for all NAD glycohydrolases and is important in regulating its activity. ADPRT activity of the enzyme was decreased by novobiocin and isonicotinic acid hydrazide. These results suggest that Mycobacterium smegmatis ADPRT could be regulated by a different way from other NADases and involved in bacterial physiological process through a post-translational modification of cytosolic proteins.

Biochemical studies with bi-resistant mutants (ethambutol plus streptomycin and isoniazid plus streptomycin) of Mycobacterium smegmatis ATCC 607.

Biochemical characteristics of bi-resistant mutants (resistant to ethambutol plus streptomycin or isoniazid plus streptomycin) of mycobacteria isolated by replica plating from Mycobacterium smegmatis ATCC were compared with those of the drug-susceptible strains. Reduced incorporation of [14C]uracil, [3H]lysine and [14C]acetate into RNA, protein and phospholipids respectively was seen in the resistant mutants. Total phosphorlipids were enhanced in ethambutol plus streptomycin resistant mutant and decreased in isoniazid plus streptomycin resistant mutant. There were similar changes in levels of individual phospholipids. The resistant mutants revealed an accumulation of phospholipids in the cell wall, and a marked decrease of phospholipids in the cell membrane in comparison to the susceptible strain. Several qualitative alterations in the polypeptide profile (with respect to number and molecular weight) of the crude protein extract and of different subcellular compartments were seen in the resistant mutants.

Phospholipids of ethambutol-susceptible and resistant strains of Mycobacterium smegmatis.

The composition, subcellular distribution and rate of synthesis of phospholipids were compared in ethambutol susceptible and resistant strains of Mycobacterium smegmatis. Significant quantitative alterations in phospholipids accompanied the acquisition of resistance, whereas fatty acyl group composition of total phospholipid remained the same in ethambutol resistant and susceptible strains. Cell wall of resistant strain exhibited an accumulation of phospholipids and a decrease in the degree of unsaturation of phospholipid fatty acyl groups. Changes in the cell wall phospholipid composition may contribute to resistance of Mycobacterium smegmatis to ethambutol.

The distribution and expression of recombinant M.smegmatis in mice receiving intranasal immunization / 重庆医科大学学报

Objective: To observe the distribution and expression of recombinant Mycobacterium smegmatis carrying the plasmid encoding human granulysin(GLS) and murine IL-12 by intranasal immunization in mice.Methods: BALB/C mice were intranasally immunized with recombinant M.smegmatis carrying the plasmid encoding green fluorescent protein(GFP).The distribution of GFP and recombinant Mycobacterium smegmatis in the lungs and spleens was detected 14 days after the first immunization.BALB/C mice were intranasally immunized three times with recombinant M.smegmatis carrying the plasmid encoding GLS and IL-12.28 days after the first immunization,the expression of GLS in tissue,levels of IL-12 in serum and SIgA in BALF(bronchoalveolar lavage fluid)were detected with immunohistochemistry and ELISA respectively.Results: The distribution of GFP and recombinant Mycobacterium smegmatis in lung and spleen was detected.The expression of GLS,the increased of IL-12 in serum and the specific SIgA in BALF were found.Conclusion: The distribution of recombinant Mycobacterium smegmatis carrying the plasmid encoding of GFP in lung and spleen is detected.The specific anti-bacterium SIgA is generated.GLS and IL-12 are expressed in BALB/C mice after intranasal immunization with recombinant Mycobacterium smegmatis carrying the plasmid encoding GLS and IL-12.The results lay the foundation for new vaccine study.

Growth of Mycobacterium smegmatis in minimal and complete media.

The growth patterns of Mycobacterium smegmatis SN2 in a minimal medium and in nutrient broth have been compared. The growth was monitored by absorbancy (Klett readings), colony forming units, wet weight and content of DNA, RNA and protein. During the early part of the growth cycle, the bacteria had higher wet weight and macromolecular content in nutrient broth than in minimal media. During the latter half of the growth cycle however, biosynthesis stopped much earlier in nutrient broth and the bacteria had a much lower content of macromolecules than in the minimal medium. In both the media, a general pattern of completing biosynthesis rapidly in the initial phase and a certain amount of cell division at a later time involving the distribution of preformed macromolecules was seen. The possible adaptive significance of this observation has been discussed.

Stimulation of valyl- and isoleucyl-tRNA synthetase reactions by polyamines.

The aminoacylation of tRNA catalysed by valyl-tRNA synthetase (EC 6.1.1.9) and isoleucyl-tRNA synthetase (EC 6.1.1.5) from Mycobacterium smegmatis is dependent on the presence of divalent metal ions. Polyamines alone, in the absence of metal ions, do not bring about aminoacylation. In the presence of suboptimal concentrations of Mg2+, polyamines significantly stimulate the reaction. Of the cations tested, only Mn2+, Co2+ and Ca2+ can partially substitute for Mg2+ in aminoacylation, and spermine stimulates aminoacylation in the presence of these cations also. At neutral pH, spermine deacylates nonenzymatically aminoacyl tRNA. AMP and pyrophosphate-dependent enzymatic deacylation of aminoacyltRNA (reverse reaction) is also stimulated by spermine. The inhibitory effect of high concentration of KCl on aminoacylation is counteracted, by spermine. The low level of activity between pH 8·5-9·0 at 1·2 mM Mg2+ is restored to normal level on the addition of spermine. The inhibitory effect of high pH on aminoacylation in the presence of low concentration of Mg2+ is also prevntedvby spemine.