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Eukaryotic cells utilize the ubiquitin （Ub） system for maintaining a balanced functioning of cellular pathways. Although the Ub system is exclusive to eukaryotes, prokaryotic bacteria have developed an armory of Ub ligase enzymes that are capable of employing the Ub systems of various hosts, ranging from plant to animal cells. These enzymes have been acquired through the evolution and can be classified into three main classes, RING （really interesting new gene）, HECT （homologous to the E6-AP carboxyl terminus） and NEL （novel E3 ligases）. In this review we describe the roles played by different classes of bacterial Ub ligases in infection and pathogenicity. We also provide an overview of the different mechanisms by which bacteria mimic specific components of the host Ub system and outline the gaps in our current understanding of their functions. Additionally, we discuss approaches and experimental tools for validating this class of enzymes as potential novel antibacterial therapy targets.

In mice treated with antibiotics to deplete commensal microbiota, there is a significant overhaul of host cellular disposition and function with CX3CRI＋ mononuclear phagocytic cells carrying pathogenic and nonpathogenic administered bacteria to the （messenteric lymph node） MLN, resulting in T cell stimulation and IgA production.

Chemotactic motility is involved in the virulence of many pathogenic bacteria. In order to understand the role of chemotactic motility of Vibrio harveyi in cellular processes and virulence, mini-TnlO/Kan transposon-induced mutants with deficient chemotactic motility were constructed, screened, and iden- tified. Sequence analysis revealed that the 465-bp fragment （GenBank accession number HM630274） fank- ing the transposon insertion site in mutant TS-CM1 had the highest identity （96.9%） with a hypothetical protein gene of V. harveyiATCC BAA-1116 and the second-highest identity （91.8%） with the pgk gene of V. parahaemolyticus RIMD 2210633. In another mutant, TS-CM2, 356 bp of transposon-flanking sequence （GenBank accession number HM630275） also showed the highest identity （94.6%） with a hypothetical pro- tein gene of V. harveyi ATCC BAA-1116 and the second-highest identity （92.4%） with the flaB gene of V. alginolyticus HY9901. Studies on virulence-related biological characteristics such as growth, motility, adhe- sion, and infectivity of the mutants showed that disruption of either the flagellin gene or energy metabolism gene led to subsequent loss of chemotactic motility and changes in growth, motility, adhesion, and viru- lence of the pathogenic E harueyi. Hence, the flagellin gene and crucial energy metabolism gene played an important role in the chemotactic motility of V. harveyi.

中国绿海龟(Chelonia mydas)繁育技术的进步促进了自然保护区内绿海龟种群规模的不断增加,细菌性病原感染成为威胁绿海龟(稚龟)繁育安全的首要问题。为深入了解中国绿海龟(稚龟)细菌性疾病流行情况,在2019—2021年对广东惠东海龟国家级自然保护区内的患病绿海龟(稚龟)进行了病原菌分离鉴定,采用16S rRNA分子鉴定结合细菌生化鉴定技术,共分离鉴定疑似病原株45株,涉及10个菌属,革兰氏染色显示均为革兰氏阴性细菌。弧菌属(Vibrio)细菌19株,占疑似病原菌的42.22%,其中溶藻弧菌(V.alginolyticus)7株,占分离弧菌的36.84%,属优势弧菌。对溶藻弧菌进行攻毒与病龟组织切片分析,结果显示,溶藻弧菌对中华草龟(Chinemys reevesii)具有较高的致病力,其LD50为2.99×106～2.59×108 cfu/mL; 分离的溶藻弧菌可以引起中华草龟肠道、肝脏和脾脏组织病理损伤。进一步分析45株病原菌对水产养殖允许使用的6种抗生素的耐药性,结果显示分离菌株对盐酸多西环素、复方新诺明具有较高的耐药性,硫酸新霉素、氟苯尼考、恩诺沙星和环丙沙星可以作为绿海龟感染的应急用药。研究表明弧菌是中国惠东海龟国家级自然保护区内绿海龟的主要病原菌,本研究较为系统地对绿海龟细菌性疾病进行的流行病学调查,为绿海龟救护提供了临床数据和理论依据。

昆明市某公园,1头亚洲象出现排便次数减少、粪便带有鲜血、四肢发抖、体温升高、触腹部坚实等症状。为找准大象病因,本实验采集该大象粪便,在云南省动物疫病预防控制中心进行试验,通过细菌分离培养、革兰氏染色镜检、选择鉴别培养基进行鉴别培养、生化试验和PCR扩增及产物测序等方法对其粪便细菌进行分离鉴定,实验结果表明:粪便中有大肠杆菌O83:H1、大肠杆菌O104:H4和产酸克雷伯菌(Klebsiella oxytoca)等多种条件致病菌; 并对其不太常见的产酸克雷伯菌进行药敏试验,该细菌对氧氟沙星、头孢曲松、头孢赛肟钠 、环丙沙星、卡那霉素、磺胺异亚唑等极度敏感; 对阿莫西林、多粘菌素B等高度敏感; 对万古霉素等中度敏感; 对甲氧嘧啶耐药。产酸克雷伯菌的动物回归试验研究结果表明:接种过菌液的小鼠表现出腹泻和食欲下降等临床症状,严重的发生死亡,解剖症状主要是肝脏部分坏死、肠道充血肿胀、肺脏有出血点,证明其对小鼠易感且具有较强的致病性,产酸克雷伯菌最小致死量(MLD)为2.5×1012 cfu/mL; 半数致死量为5×1013 cfu/mL。本次研究旨在加强对产酸克雷伯菌生理生化特性及致病性的了解,为临床诊断提供可靠的依据和有效的治疗方法。