Andrias Davidianus Research Articles

Development Problems and Suggestions for the Giant Salamander Industry

The Chinese giant salamander (<i>Andrias davidianus</i>), the American giant salamander (<i>Cryptobranchus alleganiensis</i>), and the Japanese giant salamander (<i>A. japonicum</i>) are precious aquatic protected animals that currently exist in the world. The latter two cannot be traded locally, whether wild or cultivated, and can only be protected, so they have not formed an industry. However, China allows the second generation of artificially bred offspring giant salamander to be traded and has already formed a factory scale breeding. The Chinese giant salamander has high economic value in food, health, medicine, beauty and other fields. In recent years, its artificial breeding industry has been widely developed in China and has a certain industrial scale. However, there are also many problems in the development of the giant salamander industry. In order to promote the high-quality development of the giant salamander industry and improve its quality, this article conducts research on the giant salamander industry, identifies existing problems, and provides suggestions. Firstly, this article analyzes the problems in the development process of giant salamanders from multiple perspectives, including management, service, market, research and development, and brand awareness. Secondly, corresponding industrial development strategies are proposed, including increasing regulatory efforts, enhancing service awareness, building market order, expanding sales channels, increasing research and development investment, reducing disease occurrence, extending the industrial chain, and strengthening brand awareness. Finally, the prospects for the development of the giant salamander industry are discussed.

Transcriptomic analysis of spleen-derived macrophages in response to lipopolysaccharide shows dependency on the MyD88-independent pathway in Chinese giant salamanders (Andrias davidianus)

BackgroundGram-negative bacteria are the main bacterial pathogens infecting Chinese giant salamanders (Andrias davidianus; CGS) in captivity and the wild, causing substantial economic losses in the CGS industry. However, the molecular mechanisms underlying pathogenesis following infection remain unclear.ResultsSpleen-derived macrophages from healthy CGS were isolated, cultured, and identified using density gradient centrifugation and immunofluorescence. A macrophage transcriptome database was established 0, 6, and 12 h post lipopolysaccharide stimulation using RNA-sequencing. In the final database 76,743 unigenes and 4,698 differentially expressed genes (DEGs) were functionally annotated. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment results showed that DEGs were concentrated in toll-like receptor–nuclear factor kappa B-related immune pathways. Ten DEGs were validated 12 h after lipopolysaccharide (LPS) stimulation. Although the common LPS recognition receptor toll-like receptor 4 was not activated and the key adaptor protein MyD88 showed no significant response, we observed significant up-regulation of the following adaptors: toll/interleukin-1 receptor domain-containing adaptor inducing interferon-β, tumour necrosis factor receptor-associated factor 6, and transforming growth factor-β activated kinase 1, which are located downstream of the non-classical MyD88 pathway.ConclusionsIn contrast to that in other species, macrophage activation in CGS could depend on the non-classical MyD88 pathway in response to bacterial infection. Our study provides insights into the molecular mechanisms regulating CGS antibacterial responses, with implications for disease prevention and understanding immune evolution in amphibians.

An Andrias davidianus derived composite hydrogel with enhanced antibacterial and bone repair properties for osteomyelitis treatment.

Effective antibacterial therapy while accelerating the repair of bone defects is crucial for the treatment of osteomyelitis. Inspired by the protective mechanism of Andrias davidianus, we constructed an antibacterial hydrogel scaffold with excellent rigidity and long-term slow-release activity. While retaining the toughness of the skin secretion of Andrias davidianus (SSAD), the rigidity of the hydrogel material is increased by incorporating hydroxyapatite to meet the demands of bone-defect-filling materials. It also exerted antibacterial effects via the slow-release of vancomycin from local osteomyelitis lesions. Notably, the hydrogel can also carry a high stable recombinant miR-214-3p inhibitor (MSA-anti214). By the delivery of nano vector polyvinylamine, the long-term slow-release of MSA-anti214 is achieved to promote bone repair, making this composite hydrogel a potential SSAD-based osteomyelitis alleviator (SOA). In vitro and vivo results verified that the SOA effectively eliminated Staphylococcus aureus and repaired bone defects, ultimately mitigating the progression of osteomyelitis. This composite hydrogel extends the economic application prospects of A. davidianus and has provided new insights for the treatment of osteomyelitis. The study also explored new insights for the bone filling materials of bone defection and other skeletal system diseases.

The expressions of nr0b1/2 genes in the Chinese giant salamander and their response to estradiol benzoate/17α-methyltestosterone treatment

Previously, the nr0b1 and nr0b2 genes have been identified in various animals and found to be closely associated with sex determination. In order to investigate the regulatory roles of nr0b1 and nr0b2 genes in the sex determination of Chinese giant salamander (CGS, Andrias davidianus), we obtained the full-length cDNA sequences of nr0b1 and nr0b2 through cloning, determined the characteristics of their tissue expressions and the responses of nr0b1 and nr0b2 to estradiol benzoate (EB) and 17α-methyltestosterone (MT) by using quantitative real-time PCR (qRT-PCR), and evaluated gonad development through histological sections. The full-lengths of cDNA of nr0b1/2 in C GS are separately 1278bp and 789bp. They have complete open reading frames (ORF) of 864bp and 774bp and encode 287 and 257 amino acids respectively. The 3' untranslated regions (UTR) are 276bp and 15bp, and the 5' UTR of nr0b1 is 138bp. In the 3' UTR of nr0b1, a putative polyadenylation signal (AATAAA) is identified. Tissue distribution analysis indicates that nr0b1 is mainly expressed in the pituitary, kidney, and testes, with significant differences between females (ZW-F) and males (ZZ-M) expression in the testes. On the other hand, nr0b2 is mainly expressed in the liver, followed by gonadal tissues. After immersion and feeding with EB and MT, EB's promotion on nr0b1 expression in CGS ovaries and testes is shown, by contrast MT only has a positive effect on nr0b2 in CGS testes. Histological sections show that after EB treatment, both genetic females (ZW-F) and sex-reversed females (ZZ-F) of CGS contain oogonia, indicating that EB can cause sex reversal in CGS; however, after MT treatment, no cellular morphological changes are observed either in genetic females (ZW-F) or in genetic males (ZW-M), indicating that this concentration cannot induce a shift in the sex ratio of CGS. These findings lay the foundation for further investigating the molecular mechanisms by which nr0b1/2 influence the differentiation and maintenance of CGS gonads.

Sex-Specific Lipid Profiles and Flavor Volatiles in Giant Salamander (Andrias davidianus) Tails Revealed by Lipidomics and GC-IMS

To elucidate the relationships between lipid components and odor traits, this study comparatively characterized the distinct lipid compositions and flavor volatiles in giant salamander tails of different sexes via mass-spectrometry-based lipidomics and GC-IMS. A total of 3145 fat metabolites were detected in male and female giant salamander tails, with the largest contributors being triglycerides (TGs, 840) and phosphatidylcholines (PCs, 383). Notably, the contents of PCs and TGs were greater in female tails than in male tails, and the levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were also greater in the female group. Additionally, a total of 45 volatile components were detected, namely, 14 aldehydes, 14 alcohols, 9 ketones, 3 acids, 3 esters, 1 ether, and 1 amine. Alcohols (29.96% to 34.85%) and aldehydes (21.07% to 22.75%) were the predominant volatiles. Multivariate statistical analysis revealed 22 key differential fats and 26 differential odor substances as distinguishing labels between sexes. Correlation analysis revealed that the concentrations of triethylamine, dimethyl sulfide, ethanol-D, and 3-methyl butanal-D were significantly positively correlated with the concentrations of diglyceride (DG) (26:6e), cardiolipin (CL) (59:4), acylcarnitine (AcCa) (22:4), and triglyceride (TG) (52:10) (p < 0.01). Threefold cross-validation revealed that the prediction accuracies of these differential lipids and volatile compounds for sex recognition via the random forest model were 100%. These findings might not only provide insight into the effects of sexes on the lipid and volatile profiles of giant salamander tails but also provide clues for their gender recognition.

A droplet digital PCR assay to detect Chinese rice-field eels rhabdovirus.

Chinese rice-field eels rhabdovirus (CrERV) causes haemorrhagic disease in Chinese rice-field eels (Monopterus albus), leading to significant mortality and economic losses. Sensitive detection of CrERV nucleic acids is essential to control the spread of this pathogen and to treat infected individuals. Herein, we developed an efficient and sensitive droplet digital PCR (ddPCR) method to rapidly detect and quantify CrERV. The ddPCR assay optimal conditions were an annealing temperature of 53°C, and primer and probe concentrations of 0.5 and 0.25 μM, respectively. The assay had a diagnostic sensitivity of 0.23 copies/μL, and was highly specific, showing no cross reactivity with other viruses (infectious haematopoietic necrosis virus, grass carp reovirus, spring viremia of carp virus, largemouth bass ranavirus, carp edema virus, Chinese giant salamander iridovirus, and white spot syndrome virus). Real-time quantitative PCR testing of 30 Chinese rice-field eels samples detected CrERV in 7 samples (23.3%), whereas ddPCR detected CrERV in 12 samples (40%), demonstrating its higher sensitivity. Thus, ddPCR represents an advanced method to absolutely quantify CrERV in infected fish with low virus concentrations, providing a valuable tool to manage the spread and impact of CrERV.

Characterization of NLRP3 inflammasome components in the endangered Chinese giant salamander (Andrias davidianus)

Chinese giant salamander (Andrias davidianus) is the largest extant urodela species and has unique evolutionary position. Studying the immune system of Chinese giant salamander contributes to understanding the evolution of immune systems of vertebrates. The NLR-related protein 3 (NLRP3) inflammasome comprised of NLRP3, ASC and caspase-1 play important roles in the host innate immunity. However, little is know about the NLRP3 inflammasome components in Chinese giant salamander. In this study, the NLRP3, apoptosis-associated speck-like protein (ASC) and caspase-1 (adaNLRP3, adaASC and adaCaspase-1) were characterized from Chinese giant salamander. The proteins of these three genes shared similar motifs and structures with their mammalian counterparts, with a PYD motif, a nucleotide-binding domain (NACHT) motif, and four leucine-rich repeat domain (LRR) motifs identified in adaNLRP3, a pyrin domain (PYD) motif and a caspase recruitment domain (CARD) motif in adaASC, and a CARD motif and a CASc motif in adaCaspase-1. These three genes were constitutively expressed in the skin, heart, lung, kidney, muscle, brain, spleen, and liver of Chinese giant salamander. Following Aeromonas hydrophia infection, all the three genes were up-regulated in various tissues. Molecular docking analysis revealed that the key residues involved in forming the adaNLRP3/adaASC complex were located in the PYD motifs, and that involved in forming the adaASC/adaCaspase-1 complex were located in the CARD motifs. Further analysis revealed that the hydrogen bonds and salt bridges had crucial roles in the formation of adaNLRP3/acaASC and adaASC/adaCaspase-1 complexes. To the best of our knowledge, this is the first report on the NLRP3 inflammasome components in Chinese giant salamander which will be helpful in further understanding the function of the NLRP3 inflammasome and in elucidating its role in the immune response to microbes.

Isolation and identification of Acinetobacter lwoffii from the Chinese Giant Salamander (Andrias davidianus)

This study aimed to identify the primary pathogenic bacteria responsible for the mortality of the Chinese giant salamander (Andriasd davidianus). A pathogenic bacterium was isolated from a diseased Chinese giant salamander exhibiting typical symptoms under aseptic conditions and then identified by morphological examinations, biochemical analysis, and the sequence analysis of bacterial 16S rRNA. Artificial infection testing was then conducted to determine the pathogenicity of the isolated bacteria strain. Drug susceptibility tests were conducted using the agar diffusion method. The isolated pathogenic bacteria, named DN-2, was successfully identified as Acinetobacter lwoffii. The artificial infection showed that the typical symptoms of the disease could be replicated as the ones originally occurred, and this bacterium exhibited high pathogenicity to the Chinese giant salamander. In the Chinese giant salamander, the median lethal dosage (LD50) of A. lwoffii DN-2 for A. davidianus was determined to be 4.63×104 CFU/g. Drug sensitivity testing showed that these bacteria were highly sensitive to erythromycin, gentamicin, neomycin, streptomycin, midecamycin, ciprofloxacin, piperacillin, florfenicol, doxycycline, carbenicillin, and sulfanilamide. In summary, A. lwoffii was identified as the primary pathogen responsible for the demise of A. davidianus. Our study first presents how these bacteria harm Chinese giant salamanders.

Exploration of potential antihypertensive peptides derived from farmed Chinese giant salamander (Andrias davidianus)

Exploration of potential antihypertensive peptides derived from farmed Chinese giant salamander (Andrias davidianus)

Exposure to polystyrene nanoplastics causes immune damage, oxidative stress and intestinal flora disruption in salamander (Andrias davidianus) larvae

The toxic effects of nanoparticles have been increasingly investigated, but there has been limited research on amphibians, especially those of conservation value. This study examined the effects of different concentrations (0, 0.04, 0.2, 1, 5 mg/L) of polystyrene nanoplastics (PS-NPs, 80 nm) on the short-term exposure (7 d) of Andrias davidianus. Results demonstrated the concentration-dependent enrichment of PS-NPs in the intestine. Histological lesions displayed increased hepatic macrophages with cellular rupture, broken intestinal villi, decreased cuprocytes and crypt depression. Antioxidant- and inflammation-related enzyme activities were analysed, and it was found that hepatic and intestinal MDA content and CAT activity were highest in the N-1 group and SOD activity was highest in the N-0.2 group (p < 0.05). AKP activity continued to decline, and iNOS activity was highest in the N-0.2 group (p < 0.05). il-10, tgf-β, bcl-w and txnl1 were significantly downregulated in the N-0.2 group, while il-6 and il-8 were markedly upregulated in the N-0.2 group (p < 0.05). Exposing to PS-NPs decreased probiotic bacteria (Cetobacterium, Akkermansia) and increased pathogenic bacteria (Lachnoclostridium). Our results suggest that NPs exposure can have deleterious effects on salamanders, which predicts that NPs contamination may lead to continued amphibian declines. Therefore, we strongly recommend that attention be paid to amphibians, especially endangered species, in the field of NPs.

Structural and sensory characteristics of ultrasonic assisted wet-heating Maillard reaction products of Giant salamander protein hydrolysates.

Chinese giant salamander protein hydrolysates (CGSPH) are beneficial to human health as a result of their high content of amino acids and peptides. However, the formation of bitter peptides in protein hydrolysates (PHs) would hinder their application in food industry. The ultrasound assisted wet-heating Maillard reaction (MR) is an effective way to improve the flavor of PHs. Thus, the effect of ultrasonic assisted wet-heating MR on the structure and flavor of CGSPH was investigated in the present study. The results indicated that the ultrasound assisted wet-heating MR products (MRPs) exhibited a higher degree of graft and more significant changes in the secondary and tertiary structures of CGSPH compared to traditional wet-heating MRPs. Moreover, ultrasound assisted wet-heating MR could significantly increase the content of small molecule peptides and reduce the content of free amino acids of CGSPH, which resulted in more significant changes in flavor characteristics. The changed in flavor properties after MR (especially ultrasound assisted wet-heating MRPs) were mainly manifested by a significant reduction in bitterness, as well as a significant increase in the content of aromatic aldehyde ester compounds such as furan-2-carbaldehyde, butanal, benzaldehyde, furfural, etc. CONCLUSIONS: Ultrasound assisted wet-heating MR between CGSPH and xylose could be a promising way to improve the sensory characteristics of CGSPH. © 2024 Society of Chemical Industry.

Improved Chinese Giant Salamander Parental Care Behavior Detection Based on YOLOv8.

Optimizing the breeding techniques and increasing the hatching rate of Andrias davidianus offspring necessitates a thorough understanding of its parental care behaviors. However, A. davidianus' nocturnal and cave-dwelling tendencies pose significant challenges for direct observation. To address this problem, this study constructed a dataset for the parental care behavior of A. davidianus, applied the target detection method to this behavior for the first time, and proposed a detection model for A. davidianus' parental care behavior based on the YOLOv8s algorithm. Firstly, a multi-scale feature fusion convolution (MSConv) is proposed and combined with a C2f module, which significantly enhances the feature extraction capability of the model. Secondly, the large separable kernel attention is introduced into the spatial pyramid pooling fast (SPPF) layer to effectively reduce the interference factors in the complex environment. Thirdly, to address the problem of low quality of captured images, Wise-IoU (WIoU) is used to replace CIoU in the original YOLOv8 to optimize the loss function and improve the model's robustness. The experimental results show that the model achieves 85.7% in the mAP50-95, surpassing the YOLOv8s model by 2.1%. Compared with other mainstream models, the overall performance of our model is much better and can effectively detect the parental care behavior of A. davidianus. Our research method not only offers a reference for the behavior recognition of A. davidianus and other amphibians but also provides a new strategy for the smart breeding of A. davidianus.

Screening of Chinese giant salamander meat hydrolysates with DPP-IV inhibitory activity and systematic elucidation of their hypoglycemic functions in mouse model

Screening of Chinese giant salamander meat hydrolysates with DPP-IV inhibitory activity and systematic elucidation of their hypoglycemic functions in mouse model

Andrias davidianus bone peptides alleviates hyperuricemia-induced kidney damage in vitro and in vivo

Hyperuricemia (HUA) is a vital risk factor for chronic kidney diseases (CKD) and development of functional foods capable of protecting CKD is of importance. This paper aimed to explore the amelioration effects and mechanism of Andrias davidianus bone peptides (ADBP) on HUA-induced kidney damage. In the present study, we generated the standard ADBP which contained high hydrophobic amino acid and low molecular peptide contents. In vitro results found that ADBP protected uric acid (UA)-induced HK-2 cells from damage by modulating urate transporters and antioxidant defense. In vivo results indicated that ADBP effectively ameliorated renal injury in HUA-induced CKD mice, evidenced by a remarkable decrease in serum UA, creatinine and blood urea nitrogen, improving kidney UA excretion, antioxidant defense and histological kidney deterioration. Metabolomic analysis highlighted 14 metabolites that could be selected as potential biomarkers and attributed to the amelioration effects of ADBP on CKD mice kidney dysfunction. Intriguingly, ADBP restored the gut microbiome homeostasis in CKD mice, especially with respect to the elevated helpful microbial abundance, and the decreased harmful bacterial abundance. This study demonstrated that ADBP displayed great nephroprotective effects, and has great promise as a food or functional food ingredient for the prevention and treatment of HUA-induced CKD.

Effect of psyllium husk powder on the gelation behavior, microstructure, and intermolecular interactions in myofibrillar protein gels from Andrias davidianus

The interaction between proteins and soluble dietary fibers plays a vital role in the development of animal-derived foods. Herein, the effects of different contents (0–3.0%) of round-bracted psyllium husk powder (PHP) on the gelation behavior, microstructure, and intermolecular interactions of Andrias davidianus myofibrillar protein (MP) were investigated. Rheological and chemical forces suggested that PHP (1.5%–2.0%) enhanced the functional properties of MP at low ionic strength, thereby increasing the viscoelasticity of mixed gels. SDS-PAGE revealed that PHP reinforced the cross-linking and aggregation of protein molecules. Circular dichroism spectroscopy, low-field nuclear magnetic resonance, and scanning electron microscopy demonstrated that PHP induced the transformation of α-helix (decreased by 14.85%) to an ordered β-sheet structure (increased by 81.58%), which was more favorable for the formation of dense network structure and improved (10.53%) the water retention of MP gels. This study provided new insights for PHP to effectively meliorate the heat-induced gelling properties of MP.

What’s in a name? Using species delimitation to inform conservation practice for Chinese giant salamanders (Andrias spp.)

Abstract Genetically-defined biodiversity units must align with practical conservation frameworks, and most conservation is conducted at the species level. Chinese giant salamanders have traditionally been interpreted as the single widespread species Andrias davidianus, but molecular studies have reinterpreted this taxon as representing multiple allopatric clades, and competing taxonomic hypotheses support different numbers of candidate species. We conducted species delimitation analyses using tree-based models (General Mixed Yule Coalescent, Poisson Tree Processes) and alignment-based models (Bayesian Phylogenetics and Phylogeography) to interpret diversification across Andrias within a comparative systematic framework, using 30 mitogenomes representing all recognised Chinese clades. Nearly all tested models provide support for at least seven statistically-resolved Chinese species-level lineages, and most provide support for nine species. Only four species have available names. Chinese Andrias populations are Critically Endangered, but unnamed species cannot be incorporated into national or international conservation frameworks and risk being excluded from recovery efforts. We urge taxonomists and conservation practitioners to focus more attention on the world’s largest amphibians, and non-standard taxonomic approaches may be required to name these species before they disappear.

A novel antidiabetic peptide GPAGAP from Andrias davidianus collagen hydrolysates: screening, action mechanism prediction and improving insulin resistance in HepG2 cells

A novel antidiabetic peptide GPAGAP from <i>Andrias davidianus</i> collagen hydrolysates: screening, action mechanism prediction and improving insulin resistance in HepG2 cells

Identification of Acinetobacter schindleri isolated from Chinese giant salamanders (Andrias davidianus)

At a particular aquaculture facility in Zhangjiajie in China, the Chinese giant salamander (Andrias davidianus) exhibited analogous clinical manifestations, culminating in sequential mortalities. This study used rigorous aseptic sampling methods to isolate bacteria from the affected liver of salamanders to determine the causative agent behind the decline in amphibians. A bacterial pathogen was isolated from diseased A. davidianus, and the strain was named DN-3. This isolate was subjected to bacterial identification, antibiotic susceptibility assays, reinfection experiments, and biochemical profiling. The isolated bacterial strain was definitively identified as Acinetobacter schindleri using 16S rRNA sequence analysis and biochemical identification. Antibiotic susceptibility testing revealed that this isolate was susceptible to neomycin, macrolides, doxycycline, piperacillin, nitrofurantoin, and carbenicillin. Subsequent reinfection assays, in which varying concentrations of the bacterial inoculum were administered to healthy salamanders, confirmed that the pathogen elicited varying degrees of morbidity or mortality within an eight-day observation period. The median lethal dose (LD50) of A. schindleri DN-3 for A. davidianus was calculated to be 6.25×104 CFU/mL. This result supports the significant pathogenicity of the strain for A. davidianus. The findings of this study provide empirical insights into the clinical management and epidemiological control of diseases affecting A. davidianus.

Real-Time Monitoring on the Chinese Giant Salamander Using RPA-LFD.

The Chinese giant salamander (Andrias davidianus), listed as an endangered species under "secondary protection" in China, faces significant threats due to ecological deterioration and the expansion of human activity. Extensive field investigations are crucial to ascertain the current status in the wild and to implement effective habitat protection measures to safeguard this species and support its population development. Traditional survey methods often fall short due to the elusive nature of the A. davidianus, presenting challenges that are time-consuming and generally ineffective. To overcome these obstacles, this study developed a real-time monitoring method that uses environmental DNA (eDNA) coupled with recombinase polymerase amplification and lateral flow strip (RPA-LFD). We designed five sets of species-specific primers and probes based on mitochondrial genome sequence alignments of A. davidianus and its close relatives. Our results indicated that four of these primer/probe sets accurately identified A. davidianus, distinguishing it from other tested caudata species using both extracted DNA samples and water samples from a tank housing an individual. This method enables the specific detection of A. davidianus genomic DNA at concentrations as low as 0.1 ng/mL within 50 min, without requiring extensive laboratory equipment. Applied in a field survey across four sites in Huangshan City, Anhui Province, where A. davidianus is known to be distributed, the method successfully detected the species at three of the four sites. The development of these primer/probe sets offers a practical tool for field surveying and monitoring, facilitating efforts in population recovery and resource conservation for A. davidianus.

Bacterial community analysis of the skin microbiota of cultured Chinese giant salamander infected with Ranavirus.

Skin microorganisms are an important component of host innate immunity and serve as the first line of defense against pathogenic infections. The relative abundance of bacterial species, microbial community assembly, and secretion of specific bacterial metabolites are closely associated with host health. In this study, we investigated the association between the skin microbiome and Ranavirus, and compared the bacterial community assemblage, alpha and beta diversity, and functional predictions of the skin bacterial assemblage in cultured healthy Chinese giant salamanders (Andrias davidianus) and individuals infected with Chinese giant salamander iridovirus (GSIV or ADRV). To achieve this, we employed 16S rRNA amplicon sequencing. The results identified Proteobacteria, Firmicutes, Bacteroidota, and Actinobacteriota as the dominant phyla in the diseased and healthy groups. Alpha diversity analysis indicated that the skin bacterial community in the diseased group exhibited no significant differences in bacterial species diversity and lower species richness compared to the healthy group. Beta diversity suggested that the two group bacterial community was quite different. Kyoto encyclopedia of genes and genomes (KEGG) pathway analyze and clusters of orthologous groups of proteins (COG) function predictions revealed that changes and variations occurred in the metabolic pathways and function distribution of skin bacterial communities in two groups.