Journal of Microbiology

Journal Articles

Deletion of lacD gene affected stress tolerance and virulence of Streptococcus suis serotype 2: Xiaowu Jiang , Lexin Zhu , Dongbo Zhan; J. Microbiol. 2022;60(9):948-959. Published online August 19, 2022; DOI: https://doi.org/10.1007/s12275-022-2146-4

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Abstract: Streptococcus suis type 2 (S. suis type 2, SS2), an infectious pathogen which is zoonotic and can induce severely public health concern. Our previous research identified a newly differential secreted effector of tagatose-bisphosphate aldolase (LacD) mediated by VirD4 factor within the putative type IV secretion system of SS2, whereas the functional basis and roles in virulence of LacD remain elusive. Here in this study, the LacD was found enzymatic and can be activated to express under oxidative stress. Gene mutant and its complemental strain (ΔlacD and cΔlacD) were constructed to analyze the phenotypes, virulence and transcriptomic profiles as compared with the parental strain. The lacD gene deletion showed no effect on growth capability and cells morphology of SS2. However, reduced tolerance to oxidative and heat stress conditions, increased antimicrobial susceptibility to ciprofloxacin and kanamycin were found in ΔlacD strain. Further, the LacD deficiency led to weakened invasion and attenuated virulence since an easier phagocytosed and more prone to be cleared of SS2 in macrophages were shown in ΔlacD mutant. Distinctive transcriptional profiling in ΔlacD strain and typical downregulated genes with significant mRNA changes including alcohol dehydrogenase, GTPase, integrative and conjugative elements, and iron ABC transporters which were mainly involved in cell division, stress response, antimicrobial susceptibility and virulence regulation, were examined and confirmed by RNA sequencing and real time qPCR. In summary, the
results
demonstrated for the first time that LacD was a pluripotent protein mediated the metabolic, stress and virulent effect of SS2.

Phosphorylation of tegument protein pp28 contributes to trafficking to the assembly compartment in human cytomegalovirus infection: Jun-Young Seo , Jin Ah Heo , William J. Britt; J. Microbiol. 2020;58(7):624-631. Published online June 27, 2020; DOI: https://doi.org/10.1007/s12275-020-0263-5

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Abstract: Human cytomegalovirus (HCMV) UL99 encodes a late tegument protein pp28 that is essential for envelopment and production of infectious virus. This protein is localized to the endoplasmic reticulum-Golgi intermediate compartment (ERGIC) in transfected cells but it localizes to the cytoplasmic assembly compartment (AC) in HCMV-infected cells. Trafficking of pp28 to the AC is required for the assembly of infectious virus. The N-terminal domain (aa 1-61) of pp28 is sufficient for trafficking and function of the wild type protein during viral infection. However, residues required for authentic pp28 trafficking with the exception of the acidic cluster in the N-terminal domain of pp28 remain undefined. Monitoring protein migration on SDS-PAGE, we found that pp28 is phosphorylated in the virus-infected cells and dephosphorylated in the viral particles. By generating substitution mutants of pp28, we showed that three serine residues (aa 41–43) and a tyrosine residue (aa 34) account for its phosphorylation. The mutant forms of pp28 were localized to the plasma membrane as well as the ERGIC in transfected cells. Likewise, these mutant proteins were localized to the plasma membrane as well as the AC in virus-infected cells. These results suggested that phosphorylation of pp28 contributes to its intracellular trafficking and efficient viral assembly and incorporation.

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