Choudhury Jayanta D, Pramanik Arnab, Webster Nicole S, Llewellyn Lyndon E, Gachhui Ratan, Mukherjee Joydeep
School of Environmental Studies, Jadavpur University, Kolkata, 700 032, India.
Mar Biotechnol (NY). 2015 Aug;17(4):463-78. doi: 10.1007/s10126-015-9627-y. Epub 2015 Apr 3.
Sponge diseases have increased dramatically, yet the causative agents of disease outbreaks have eluded identification. We undertook a polyphasic taxonomic analysis of the only confirmed sponge pathogen and identified it as a novel strain of Pseudoalteromonas agarivorans. 16S ribosomal RNA (rRNA) and gyraseB (gyrB) gene sequences along with phenotypic characteristics demonstrated that strain NW4327 was most closely related to P. agarivorans. DNA-DNA hybridization and in silico genome comparisons established NW4327 as a novel strain of P. agarivorans. Genes associated with type IV pili, mannose-sensitive hemagglutinin pili, and curli formation were identified in NW4327. One gene cluster encoding ATP-binding cassette (ABC) transporter, HlyD and TolC, and two clusters related to the general secretion pathway indicated the presence of type I secretion system (T1SS) and type II secretion system (T2SS), respectively. A contiguous gene cluster of at least 19 genes related to type VI secretion system (T6SS) which included all 13 core genes was found. The absence of T1SS and T6SS in nonpathogenic P. agarivorans S816 established NW4327 as the virulent strain. Serine proteases and metalloproteases of the classes S8, S9, M4, M6, M48, and U32 were identified in NW4327, many of which can degrade collagen. Collagenase activity in NW4327 and its absence in the nonpathogenic P. agarivorans KMM 255(T) reinforced the invasiveness of NW4327. This is the first report unambiguously identifying a sponge pathogen and providing the first insights into the virulence genes present in any pathogenic Pseudoalteromonas genome. The investigation supports a theoretical study predicting high abundance of terrestrial virulence gene homologues in marine bacteria.
海绵疾病急剧增加，但疾病暴发的病原体一直未得到鉴定。我们对唯一已确认的海绵病原体进行了多相分类分析，并将其鉴定为食琼脂假交替单胞菌的一个新菌株。16S核糖体RNA（rRNA）和gyrB基因序列以及表型特征表明，NW4327菌株与食琼脂假交替单胞菌关系最为密切。DNA-DNA杂交和电子基因组比较确定NW4327为食琼脂假交替单胞菌的一个新菌株。在NW4327中鉴定出与IV型菌毛、甘露糖敏感血凝素菌毛和卷曲菌毛形成相关的基因。一个编码ATP结合盒（ABC）转运蛋白、HlyD和TolC的基因簇，以及两个与一般分泌途径相关的基因簇，分别表明存在I型分泌系统（T1SS）和II型分泌系统（T2SS）。发现了一个至少由19个与VI型分泌系统（T6SS）相关的基因组成的连续基因簇，其中包括所有13个核心基因。非致病性食琼脂假交替单胞菌S816中不存在T1SS和T6SS，这确定NW4327为致病菌株。在NW4327中鉴定出S8、S9、M4、M6、M48和U32类的丝氨酸蛋白酶和金属蛋白酶，其中许多可以降解胶原蛋白。NW4327中的胶原酶活性以及非致病性食琼脂假交替单胞菌KMM 255(T)中不存在该活性，进一步证明了NW4327的侵袭性。这是第一份明确鉴定海绵病原体并首次深入了解任何致病性假交替单胞菌基因组中存在的毒力基因的报告。该研究支持了一项理论研究，该研究预测海洋细菌中陆地毒力基因同源物的丰度很高。
