Ca. Endozoicomonas cretensis: A Novel Fish Pathogen Characterized by Genome Plasticity

Abstract

Endozoicomonas bacteria are generally beneficial symbionts of diverse marine invertebrates including reef-building corals, sponges, sea squirts, sea slugs, molluscs, and Bryozoans. In contrast, the recently reported Ca. Endozoicomonas cretensis was identified as a vertebrate pathogen, causing epitheliocystis in fish larvae resulting in massive mortality. Here, we described the Ca. E. cretensis draft genome, currently undergoing genome decay as evidenced by massive insertion sequence (IS element) expansion and pseudogene formation. Many of the insertion sequences are also predicted to carry outward-directed promoters, implying that they may be able to modulate the expression of neighbouring coding sequences (CDSs). Comparative genomic analysis has revealed many Ca. E. cretensis-specific CDSs, phage integration and novel gene families. Potential virulence related CDSs and machineries were identified in the genome, including secretion systems and related effector proteins, and systems related to biofilm formation and directed cell movement. Mucin degradation would be of importance to a fish pathogen, and many candidate CDSs associated with this pathway have been identified. The genome may reflect a bacterium in the process of changing niche from symbiont to pathogen, through expansion of virulence genes and some loss of metabolic capacity.

The Alteration of Intestinal Microbiota Profile and Immune Response in Epinephelus coioides during Pathogen Infection

“…In addition, Terrisporobacter was formerly known as a pathogen in humans [ 74 ]. The genera Enterovibrio, Delftia, Endozoicomonas and Ruminococcus were abundant in the Vibrio group; these genera are opportunistic bacterial pathogens in both humans and fish [ 75 , 76 , 77 , 78 , 79 , 80 ]. After infection with GIV, the intestinal microbiota was associated with a wide range of Aureispira, Eubacterium hallii, Bacteroides, Parasutterella, Rubritalea and Fusicatenibacter .…”

A microbial factory for defensive kahalalides in a tripartite marine symbiosis

“…E. kahalalidefaciens" genome (fig. S8), we looked for signs of increased genome plasticity (33,34) and intragenome genetic exchange. Briefly, we segmented the genome into 150-bp fragments, produced a whole-genome identity dot plot by comparing all fragments, and searched for genomic loci that contain a high density of matched fragment pairs (>60% sequence identity).…”

Epitheliocystis in wild marine fishes and its relation with anthropogenic pollution

“…This, however, would be harder to evaluate as little is still known about how fish acquire the obligate intracellular bacteria; vertical or horizontal transmission and/or the utilization of a reservoir such as invertebrate or protist hosts have all been proposed (Katharios et al ., 2015; Qi et al ., 2018; Stride et al ., 2014). In addition, epitheliocystis can be caused by a diverse range of bacteria from different phyla (Katharios et al ., 2015; Mendoza et al ., 2013; Qi et al ., 2018), with chlamydial or chlamydia‐like organisms as common causative agents (Blandford et al ., 2018; Stride et al ., 2014). Determination of the causative agent in the case of sandperch and rockfish was beyond the goals of our present study and more research is needed to gain a deeper understanding of the interplay between these bacteria and their hosts, their natural distribution in the environment and how this can change in response to stressors, such as pollutants.…”