[Effect of Lipoteichoic Acid Synthesis-Related Gene dltD on Acid Tolerance of Highly Cariogenic Strains of Streptococcus mutans].

Objective: To study the role and possible mechanism of dltD in the acid tolerance of Streptococcus mutans 593 (SM593), and to provide a theoretical basis for the ecological prevention and control of dental caries by constructing the dltD gene deletion strain of SM593 (SM593-ΔdltD). Methods: 1) SM593-Δ dltD was constructed by homologous recombination. 2) The growth curve of SM593 dltD and SM593-Δ dltD under different pH culture conditions was drawn by the automatic growth curve analyzer to compare their acid tolerance. Colony forming unit (CFU) at different time points was used to calculate the survival rate and to compare the acid tolerance response (ATR) of SM593 and SM593-Δ dltD. 3) Under different pH conditions, glycolysis experiments, proton permeability test and H +-ATPase activity test were conducted to make preliminary exploration into the mechanisms of how dltD gene deletion may affect acid tolerance. Results: 1) PCR and sequencing results showed that the SM593-Δ dltD was constructed successfully. 2) With decreasing pH value of the culture medium, the growth of SM593-Δ dltD slowed down. When the pH value of the culture medium was 5.0, SM593-Δ dltD was not allowed to grow, and its acid tolerance was lower than that of SM593. Compared with SM593, the ATR capability of SM593-Δ dltD was decreased. 3) SM593 dltD and SM593-Δ dltD did not show obvious difference in their glycolysis ability under different pH conditions. Compared with SM593 dltD, the proton permeability of SM593-Δ dltD under different pH conditions was increased significantly (P<0.05), and H +-ATPase activity decreased significantly (P<0.05). Conclusion: Compared with SM593 dltD, SM593-Δ dltD showed obvious decrease in acid tolerance, which may be caused by the significant increase in proton permeability and significant decrease in the H +-ATPase activity induced by the deletion of the dltD gene, hence reducing its ability to maintain intracellular pH homeostasis.

A broad-range survey of ticks from livestock in Northern Xinjiang: changes in tick distribution and the isolation of Borrelia burgdorferi sensu stricto.

BACKGROUND: Borreliosis is highly prevalent in Xinjiang Uygur Autonomous Region, China. However, little is known about the presence of Borrelia pathogens in tick species in this region, in addition Borrelia pathogens have not been isolated from domestic animals. METHODS: We collected adult ticks from domestic animals at 19 sampling sites in 14 counties in northern Xinjiang from 2012 to 2014. Ticks were identified to species by morphology and were molecularly analysed by sequences of mitochondrial 16S rDNA gene; 4-8 ticks of each species at every sampling site were sequenced. 112 live adult ticks were selected for each species in every county, and were used to culture Borrelia pathogens; the genotypes were then determined by sequences of the 5S-23S rRNA intergenic spacer and the outer surface protein A (ospA) gene. RESULTS: A total of 5257 adult ticks, belonging to four genera and seven species, were collected. Compared with three decades ago, the abundance of the five common tick species during the peak ixodid tick season has changed. Certain tick species, such as Rhipicephalus turanicus (Rh. turanicus), was found at Jimusaer, Yining, Fukang, and Chabuchaer Counties for the first time. Additionally, the sequence analyses showed that the Hyalomma asiaticum (Hy. asiaticum), Haemaphysalis punctata (Ha. punctata), and Dermacentor marginatus (D. marginatus) that were collected from different sampling sites (≥3 sites) shared identical 16S rDNA sequences respectively. For the tick species that were collected from the same county, such as Hy. asiaticum from Shihezi County and Rh. turanicus from Yining County, their 16S rDNA sequences showed genetic diversity. In addition, sixteen Borrelia isolates were found in Hy. asiaticum, Ha. punctata, D. marginatus and Rh. turanicus, which infested cattle, sheep, horse and camel in Yining, Chabuchaer, Shihezi and Shawan Counties. All of the isolates were genetically identified as B. Burgdorferi sensu stricto. CONCLUSIONS: Warmer and wetter climate may have contributed to the altered distribution and abundance of the five most common ticks in northern Xinjiang. The genetic analyses showed that certain tick species, such as Hy. asiaticum or Rh. turanicus, exhibit genetic commonness or diversity. Additionally, this study is the first to isolate B. burgdorferi sensu stricto in Hy. asiaticum asiaticum, H. punctata, D. nuttalli and D. marginatus ticks from domestic animals. These ticks may transmit borreliosis among livestock.

Changes of mitochondrial ultrastructures and function in central nervous tissue of hens treated with tri-ortho-cresyl phosphate (TOCP).

Tri-ortho-cresyl phosphate (TOCP), an organophosphorus ester, is capable of producing organophosphorus ester-induced delayed neurotoxicity (OPIDN) in humans and sensitive animals. The mechanism of OPIDN has not been fully understood. The present study has been designed to evaluate the role of mitochondrial dysfunctions in the development of OPIDN. Adult hens were treated with 750 mg/kg·bw TOCP by gavage and control hens were given an equivalent volume of corn oil. On day 1, 5, 15, 21 post-dosing, respectively, hens were anesthetized by intraperitoneal injection of sodium pentobarbital and perfused with 4% paraformaldehyde. The cerebral cortex cinerea and the ventral horn of lumbar spinal cord were dissected for electron microscopy. Another batch of hens were randomly divided into three experimental groups and control group. Hens in experimental groups were, respectively, given 185, 375, 750 mg/kg·bw TOCP orally and control group received solvent. After 1, 5, 15, 21 days of administration, they were sacrificed and the cerebrum and spinal cord dissected for the determination of the mitochondrial permeability transition (MPT), membrane potential (Δψ(m)) and the activity of succinate dehydrogenase. Structural changes of mitochondria were observed in hens' nervous tissues, including vacuolation and fission, which increased with time post-dosing. MPT was increased in both the cerebrum and spinal cord, with the most noticeable increase in the spinal cord. Δψ(m) was decreased in both the cerebrum and spinal cord, although there was no significant difference in the three treated groups and control group. The activity of mitochondrial succinate dehydrogenase assayed by methyl thiazolyl tetrazolium (MTT) reduction also confirmed mitochondrial dysfunctions following development of OPIDN. The results suggested mitochondrial dysfunction might partly account for the development of OPIDN induced by TOCP.

[Cellular ultrastructural changes of bone marrow of patients with hemorrhagic fever with renal syndrome].

BACKGROUND: To observe cytopathogenic effect of Hantaan virus (HV) on cultured human bone marrow cells. METHODS: Light and transmission electron microscopy and direct immunofluorescent technique were applied to study cellular structure especially ultrastructural changes of bone marrow cells from patients with Hantaan virus infection. Bone marrow cells of one healthy volunteer were also studied as control. RESULTS: The antigen of HV was found in bone marrow cells of 20 of 27 HFRS patients by the aid of direct immunofluorescent technique. It was found that the granulocytes had the highest percentage of HV antigen positive cells (76%), followed by monocytes (65%), lymphocytes (40%), megakaryocytes (20%) and the lowest was found in erythrocytes (3.7%). The injury of cell membrane after infection with HV was significantly more severe than that in the control group under the light and electron microscopy. CONCLUSION: This study demonstrated that HV could attack human bone marrow cells and cause cytopathogenic effect on them.