Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

The genus Aeromonas belongs to the Aeromonadaceae family and comprises a group of Gram-negative bacteria widely distributed in aquatic environments, with some species able to cause disease in humans, fish, and other aquatic animals. However, bacteria of this genus are isolated from many other habitats, environments, and food products. The taxonomy of this genus is complex when phenotypic identification methods are used because such methods might not correctly identify all the species. On the other hand, molecular methods have proven very reliable, such as using the sequences of concatenated housekeeping genes like gyrB and rpoD or comparing the genomes with the type strains using a genomic index, such as the average nucleotide identity (ANI) or in silico DNA–DNA hybridization (isDDH). So far, 36 species have been described in the genus Aeromonas of which at least 19 are considered emerging pathogens to humans, causing a broad spectrum of infections. Having said that, when classifying 1852 strains that have been reported in various recent clinical cases, 95.4% were identified as only four species: Aeromonas caviae (37.26%), Aeromonas dhakensis (23.49%), Aeromonas veronii (21.54%), and Aeromonas hydrophila (13.07%). Since aeromonads were first associated with human disease, gastroenteritis, bacteremia, and wound infections have dominated. The literature shows that the pathogenic potential of Aeromonas is considered multifactorial and the presence of several virulence factors allows these bacteria to adhere, invade, and destroy the host cells, overcoming the immune host response. Based on current information about the ecology, epidemiology, and pathogenicity of the genus Aeromonas, we should assume that the infections these bacteria produce will remain a great health problem in the future. The ubiquitous distribution of these bacteria and the increasing elderly population, to whom these bacteria are an opportunistic pathogen, will facilitate this problem. In addition, using data from outbreak studies, it has been recognized that in cases of diarrhea, the infective dose of Aeromonas is relatively low. These poorly known bacteria should therefore be considered similarly as enteropathogens like Salmonella and Campylobacter.

An Update on the Genus Aeromonas: Taxonomy, Epidemiology, and Pathogenicity

The immune system is composed of two subsystems-the innate immune system and the adaptive immune system. The innate immune system is the first to respond to pathogens and does not retain memory of previous responses. Innate immune responses are evolutionarily older than adaptive responses and elements of innate immunity can be found in all multicellular organisms. If a pathogen persists, the adaptive immune system will engage the pathogen with specificity and memory. Several components of the adaptive system including immunoglobulins (Igs), T cell receptors (TCR), and major histocompatibility complex (MHC), are assumed to have arisen in the first jawed vertebrates-the Gnathostomata. This review will discuss and compare components of both the innate and adaptive immune systems in Gnathostomes, particularly in Chondrichthyes (cartilaginous fish) and in Osteichthyes [bony fish: the Actinopterygii (ray-finned fish) and the Sarcopterygii (lobe-finned fish)]. While many elements of both the innate and adaptive immune systems are conserved within these species and with higher level vertebrates, some elements have marked differences. Components of the innate immune system covered here include physical barriers, such as the skin and gastrointestinal tract, cellular components, such as pattern recognition receptors and immune cells including macrophages and neutrophils, and humoral components, such as the complement system. Components of the adaptive system covered include the fundamental cells and molecules of adaptive immunity: B lymphocytes (B cells), T lymphocytes (T cells), immunoglobulins (Igs), and major histocompatibility complex (MHC). Comparative studies in fish such as those discussed here are essential for developing a comprehensive understanding of the evolution of the immune system.

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A Comparison of the Innate and Adaptive Immune Systems in Cartilaginous Fish, Ray-Finned Fish, and Lobe-Finned Fish

Pattern recognition receptors (PRRs) and their signaling pathways have essential roles in recognizing various components of pathogens as well as damaged cells and triggering inflammatory responses that eliminate invading microorganisms and damaged cells. The zebrafish relies heavily on these primary defense mechanisms against pathogens. Here, we review the major PRR signaling pathways in the zebrafish innate immune system and compare these signaling pathways in zebrafish and humans to reveal their evolutionary relationship and better understand their innate immune defense mechanisms.

/pdf/pattern-recognition-receptors-in-zebrafish-provide-56i8k4pd17.pdf

Pattern recognition receptors in zebrafish provide functional and evolutionary insight into innate immune signaling pathways.

https://digital.csic.es/bitstream/10261/177208/3/MIMM-D-15-00429R1%20.pdf

Polarization of immune responses in fish: The 'macrophages first' point of view.

Toll-like receptor recognition of bacteria in fish: ligand specificity and signal pathways.

Label-free proteomic analysis of intestinal mucosa proteins in common carp (Cyprinus carpio) infected with Aeromonas hydrophila.

Expression patterns of Toll-like receptors in natural triploid Carassius auratus after infection with Aeromonas hydrophila.

Qihe Carassius auratus is the territorial Carassius auratus, which is known as for its limited distribute in Qihe River (mainly distributed in Henan province, China), this species is natural triploid in China. In this study, the complete mitochondrial genome sequence of Carassius auratus in Qihe River has been obtained with PCR. The gene composition and arrangement of mitochondrial genome sequence of this species are similar to most of other vertebrates', which contains 22 tRNA genes, 13 protein-coding genes, 2 rRNA genes, and a non-coding control region with total length of 16,580 bp. Most of genes are encoded on Heavy-Strand (H-strand), exclude eight tRNA and ND6 genes, which are encoded on Light-Strand (L-strand). The bias of G and C has been found in different regions/genes and different statistic results. The complete mitochondrial genome sequence of this species would contribute to better understand population genetics, conservation, and the evolution of natural triploid.

The complete mitogenome of natural triploid Carassius auratus in Qihe River

Bellamya purificata is a widely distributed Chinese freshwater snail. It plays a significant role in ecosystem services. However, its natural habitats are under severe threat due to fragmentation and loss. In order to estimate the genetic diversity and population structure of B. purificata, 182 individuals from eight locations throughout its distribution across China were sampled. Seven microsatellite loci and the mitochondrial COI gene were genotyped. Our results showed that (1) the genetic diversity of B. purificata was high in all studied populations; (2) a low level of genetic differentiation existed among the eight populations with little restriction to gene flow; (3) no clear geographic structure was revealed by either Bayesian clustering, haplotype networks or AMOVA; (4) effective population size (Ne) was moderate to high for all studied populations. The results of Bayesian Skyline plot analysis detected unstable population sizes through time for most populations. Passive dispersal during flooding events, zoochoric dispersal, possibly anthropogenic translocations and the large population sizes might be the major reasons for the lack of differentiation among Chinese B. purificata populations.

The perplexing population genetic structure of Bellamya purificata (Gastropoda: Viviparidae): low genetic differentiation despite low dispersal ability

Chuanjiang Zhou

Papers

Toll-like receptor recognition of bacteria in fish: ligand specificity and signal pathways.

Label-free proteomic analysis of intestinal mucosa proteins in common carp (Cyprinus carpio) infected with Aeromonas hydrophila.

Expression patterns of Toll-like receptors in natural triploid Carassius auratus after infection with Aeromonas hydrophila.

The complete mitogenome of natural triploid Carassius auratus in Qihe River

The perplexing population genetic structure of Bellamya purificata (Gastropoda: Viviparidae): low genetic differentiation despite low dispersal ability