Application value of tongue coating microflora in integration of traditional Chinese medicine and modern medicine

Juan Wu, Jun Qian, Li-Yun Shi, Zhen Zhan, Jun-Feng Zhang*

1.School of Medicine & Holistic Integrative Medicine, Nanjing University of Chinese Medicine, Nanjing, China

2.School of Chinese Medicine & Integration of traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing, China

Abstract

Key words: Tongue coating, Microflora, Integration of traditional and western medicine

Background

Holistic view is the clinical feature of traditional Chinese medicine (TCM), and TCM holds that tongue is a holographic element for observing human body.Tongue image can reflect visceral lesions quickly and accurately.Thus, tongue diagnosis has been paid much more attention by TCM physicians and plays a key role in syndrome differentiation and treatment [1].In the process of embryogenesis, the epithelium of the tongue dorsum and digestive tract originate from the same endoderm, and their functions are closely interrelated.As the theory of traditional Chinese medicine says "the tongue is the outer margin of the spleen and stomach, and the tongue coating is the mirror of the spleen and stomach" [2].In other words, tongue coating provides the mediciners with a silent visible sign of the body health and diseases, and it is easy and quick to apply and observe.The tongue coating is a visible layer adherent to the tongue dorsum, and is made up of esquamated epithelial cells, infiltrated inflammatory cells, metabolites, and microorganisms.The coating nature can be thin, thick, or exfoliating, while the coating color can be white, yellow, gray, or black.TCM holds that the change of tongue coating reflects the pathophysiological status, and observating tongue coating is a valuable auxiliary diagnosis tool in many diseases [3].Furthermore, the previous investigation showed that the formation of tongue coating was aあected by many factors, such as oral hygiene, smoking, dentures, periodontal status and dietary habits.Oral hygiene was the strongest determinant [4].Thus, tongue coating microflora may play a key role in the formation of tongue coating.Here supposed that combination of the feaure of tongue coatings and their microflora provide a more intricate value in diagnosis of systemic diseases, espacially the digestive diseases.

As everyone knows, the gastrointestinal tract (oral cavity, oesophagus, stomach, small intestine, colon and rectum) harbors a great deal of microorganisms.With the rapid development of the next generation sequencing, explosive studies confirmed that human microbiota play a central role in metabolism, immune modulation, development of diseases by producing short chain fatty acids (acetic acid, propionic acid, butyric acid) and metabolism of amino acid (tryptophan, tyrosine) [5].Many clinical and laboratory evidencs found the obvious gut microbial alternation in many systmic diseases, such as digestive cancers (gastric cancer, colorectal cancer, liver cancer, pancreatic cancer), metabolic diseases (diabetes, hypertension), respiratory diseases and neurodegenerative diseases.The regulation of gut microbiome could significantly improve disease conditions [6].Based on these reliable evidences, lung-intestine axis [7], gutbrain axis [8], gut-brain-liver axis [9] and gutkidney axis [10] were established to explain the clinical complications and greatly promoted clinical progress.These axises are similar to the relationship between TCM Spleen and Heart, Liver, Lung and Kidney.Ma et al [11] reviewed the underlying association between gut microbiota and Spleen-invigorating herbs / prescriptions could promote the recovery of gut microflora.It can be assumed that gut microbiota be the functional material of TCM Spleen and be a mirror to reflecting the physiological homeostatic state.

The latest meta-analysis showed the diあerence and interaction between oral and intestinal microbiome, and more oral microbiota could appear in the stool when the systemic diseases happened, such as rheumatoid arthritis, diabetes mellitus and colorectal cancer [12,13].Since TCM holds that tongue coating be the outward manifestation of Spleen-Stomach, the tongue coating microbiota may be correlated to the gut microbiome [14].A large number of microorganisms inhabit the oral cavity, and many reports showed that the oral microbiota was not only related with oral diseases, but also related with other systemic diseases including cardiovascular disorders, metabolic disorders and malignant tumors [15].The tongue dorsum is also covered with abundant filamentous papillae, which greatly enlarges the surface area and facilitates the microbial reproduction and growth [16].Herein, the present study reviewed the applicating value of tongue coating microbiota in tongue coating variation, diagnosis, syndrome differention and therapy, and aimed to promote the scientific advancement of tongue coating microbiota in the crossover study of holistic integrative medicine.

1.Structural status of the tongue coating microbiota in the oral cavity

It has long been concerned that oral symptoms are a precursor to systemic diseases [17].Since the tongue is the largest organ in the mouth, TCM tongue diagnosis originates from the observation of tongue coating.And it has became a unique diagnosis method in TCM clinical practices [18].Recently, the "focal infection theory" re-emerged and was widely concerned, and the theory believes that the association between oral infection and secondary systemic diseases is due to metastatic infection involving microbes, metastatic damage, toxins, and metastatic inflammation, inflammatory factors [15].When the oral micro-ecological imbalance comes along, it can not only induce a variety of oral chronic infectious diseases such as dental caries, periodontal disease, mucosal lesions, but also participate in the occurrence and progression of systemic diseases and become an important indicator of systemic disease warning [19].

The complex oral cavity covers teeth, sulcus, tongue, buccal mucosa, hard palate, soft palate and other parts.The tongue surface includes dorsum, ventral and the lateral surfaces.Since the tongue coating is a layer of moss on the dorsum of the tongue.It should be noted that the flora in tongue coating is basically the same as that in the tongue dorsum.Each part inhabits a unique microbial community, which is closely related to living habits and health status.Mager et al [20] used DNA hybridization to investigate the distribution and relative abundance of 40 bacteria in 8 diあerent oral sites and saliva in 225 healthy volunteers.According to the similarity of the flora community of each site (＞85%), the 8 sites were divided into two clusters: the Cluster 1 consists of 3 sites (saliva, lateral and dorsal tongue surfaces), and the Cluster 2 includes the remaining 6 sites (vestibular lip, gingiva, floor of the mouth, buccal, tongue ventral, hard palate).Tanner et al [21] used DNA hybridization to observe the distribution 38 bacterial species in the teeth and tongue coating of 171 children aged from 6 to 36 months.They found that the flora of teeth was highly correlated with that of the tongue coating, especially in children less than 18 months.Most strains were detected more frequently from the tongue coating than the tooth, suggesting that the tongue coating be a potential plague-related microbial pool.Ren et al [22] used high-throughput sequencing to analyze microbiomes in plaque, saliva and tongue coating of 10 preschool children, and defined the operational taxonomic unit (OTU) in 80% of the samples as the core OTUs.Total 161 core OTUs have significant niche diあerences in plaque, saliva, and tongue coating, and tongue coating and saliva share the most core flora.The results indicated that the saliva flora might be mainly from the tongue coating flora at genus level, and colonizing microbes on tongue coating might be more stable than those in the flowing saliva.These results suggested that the tongue coating be the origin area and an important distributing center for the oral flora.

2.Microbal alteration in different tougue coatings

The variable tongue coatings provide much diagnosis information for TCM treatment, but the detailed biological mechanism is still unclear.Revealing the underlying mechanism of the formation of tongue coatings is an important part of the TCM modernization research.Our previous review [23] proposed that the change of tongue coating be related to the differential salivary components, the different expression levels of apoptosisrelated genes in tongue mucosa.The further studies found that the important bacterial component lipopolysaccharide (LPS) could inhibit tongue coating-related cell apoptosis in serum environment [24], but could promote tongue coating-related cell apoptosis in serumwithdrawal environment [25].The proteomics analysis showed that the saliva and serum had about 30% of similar proteins, but had diあerent richness of many proteins [26].Saliva provides an acquired biofilm and nutrient source for the oral flora, and there are more than 700 bacteria species in the oral cavity.Due to the limited culture conditions, less than 50% of the oral flora could be cultured in the laboratory.The great development of high-throughput sequencing technology with uncultivated dependence has led to the rapid development of microbiom research [27], and provides a new method for studying the biological mechanism of microbes in the formation of tongue coating.For example, Cheng et al [28] observed 12 phyla, 23 classes, 39 orders, 66 families, 133 genera, and 246 species in three kinds of coatings, including pathological yellow-greasy coating, physiological yellow-greasy coating and healthy white-thin coating.And the results presented that the abundances of two phyla (Proteobacteria, Actinobacteria) and three genera (Neisseria, Veillonella and Haemophilus) were significantly different between yellowgreasy coating and healthy white-thin coating.The results suggested that the tongue coating flora be related to pathological status.

According to the TCM theory of tongue coating, the change of tongue coating can particularly reflect the functional status of the digestive system, so many researches of the tongue coating microbiota focused on the digestive diseases in the past years.TCM thinks that the white-greasy coating and yellow coating represent the cold syndrome and heat syndrome, respectively, and distinct therapeutic methods are applied to treat the same disease.Jiang et al [29] studied the microbial composition of two typical coatings in the patients with chronic gastritis, and found that 755 OTUs had significant differences, including 61 known genera and 49 known species.It was notable that the two types of tongue coating had a significantly different symbiotic relationship.Ye et al [30] found that Bacillus might be a potential marker of yellow coating in the patients with chronic erosive gastritis, and Bacillus disappeared in the labortory culture medium when the yellow coating became thin coating after the treatment with Banxia Xiexin Decoction for two courses.Wang et al [31] found that keratinized epithelial cells were the major exfoliated cells in greasy coating in patients with chronic atrophic gastritis, which had a small morphology with blurred or disappeared nucleus, while the incompletely keratinized cells had a large round or elliptical condensed nucleus in the non-greasy tongue coating.The patients with chronic atrophic gastritis had a lower abundance of Streptococcus in tongue coating than the healthy controls.And comparison with the non-greasy coating in the patients with chronic atrophic gastritis, the patients' greasy coating had lower abundances of Provotella 7 and Veillonella but had a higher abundance of Moraxella.It was interesting that the expression of E-cadherin and intercellular adhesion factor-1 increased in the greasy coating than that in the non-greasy coating.These results suggested that the tongue coating microbes were involved in the maturation and apoptosis of the tongue dorsum mucosal epithelial cells.Thus, it is worthy of further study on the interaction between micobiota and the gene expression in the process of tongue coating alteration.

TCM holds that the transformation of tongue coatings could reflect the rise and fall of Stomach-Qi and severity of pathogenic evils.Cui et al [32] found that the relative abundance of Campylobacter concisus significantly increased with the progression of gastritis, chronic atrophic gastritis, and intestinal metaplasia both in the tongue coating and in the gastric mucosa.Zhao et al [33] found significant alteration of tongue coating microbiome and metabolism in patients with chronic hepatitis B (CHB).Compared with white tongue coating of the CHB patients, the serum titer of hepatitis B virus (HBV) DNA was higher, the significantly reduced Bacteroidetes and significantly increased Proteobacteria were observed in the yellow coating of CHB patients.And the abundance of Neisseriaceae was positively correlated with serum HBVDNA levels.These results suggested that the tongue coating microbiome can reflect the progress stage and severity of the disease.Yang Yunfeng, a famous master in Qing Dynastys, in his famous book, LIN ZHENG YAN SHE FA (Clinical examination of the tongue), proposed that yellow tongue coating reflectd the development of Spleen-Stomach diseases, especially indicated the excessive pathogenic Qi in the meridians of Spleen-Stomach, and Xiehuangsan decoction would be eあective [34].The modern clinical investigations showed that Xiehuangsan decoction was more eあective than combination of Ribavirin and Vitamin C in 60 child patients with hand foot and mouth disease, whose tongue coating was typically yellow and thick [35].Thus, observing tongue coating may provide a new approach for modern precision medicine, and investigating the underlying mechanism will interpret the biological basis for syndrome differentiation through observing tongue coating performance and greatly promote the development of integration of traditional Chinese and modern medicine.

TCM theory believes that white tongue coating indicating cold syndrome, yellow indicating heat syndrome, the thin suggesting the disease is in exterior, and the dense suggesting the disease is in the interior.Thus, the diagnosis connotation of coating color and coating thickness has a feature with relativity.The different type of tongue coating may have a unique microbiome compostion, our previous study [36] also found that the symbiotic relationship of these microbiome was also different, significant negative correlations were more popular between diあerent coating types than that within the special coating.And a predictive function of microflora (purine metabolism) of gastric cancer (GC) patients with yellow coating was significantly higher than that in the GC patients with white coating, and this predictive function was consistent with serum uric acid levels.Furthermore, correlation analysis showed that white-thick coating had the most complicated symbiotic relationship in the four common types of tongue coatings (white-thin, white-thick, yellow-thin and yellow-thick) in the GC patients [37].Therefore, the commensal relationship may also participate in the formation of tongue coatings and be of great importance in the diagnosis of systemic diseases at least in the digestive system diseases.

3.Potential diagnostic value of coating flora in disease and TCM syndrom diあerentiation

Tongue diagnosis is the characteristic and pivotal content in guiding the TCM clinical syndrome diあerentiation and treatment.The tongue coating is an important part of TCM tongue diagnosis.It is regarded as the "Window" and "Thermograph" of human pathophysiological state.Studying the tongue coating microbiome can not only enrich the theory of tongue diagnosis, but also provide an objective marker for disease diagnosis.

Modern TCM diagnosis includes diseases diagnosis and discriminating syndrome differentiation (also refers to TCM ZHENG).Some TCM Masters think that syndrome be subordinate to disease, and it is reasonable to carry out syndrome diagnosis and treatment based on the disease [38].Therefore, many scholars believed that TCM syndrome differentiation reflects an alternative paradigm of precision medicine.The clinical research of TCM should be based on the combination of disease and syndrome differentiation [39,40].Therefore, the application of systems biology and other multidisciplinary methods will be a meaningful approach to reveal the biological mechanism of TCM syndrome's formation, and to understand TCM syndrome differentiation and treatment.

Recently, more and more evidences sprang up to prensent the potential value of tongue coating flora in the diagnosis of many diseases.Sun et al [41] developed a microbial population analysis method based on genus-specific multi-factor amplification and ligation-based sequencing.More than 600 bacterial species were detected in tongue coating of lung cancer patients, and 27 pairs of primers with genus specific were designed for confirming the reliability of the high-throughput sequencing microbial results.Therefore, high-throughput sequencing to detect the tongue coating microbiomes has begun to be widely used.Chen et al [42] found that the main coating bacteria in patients with coronary heart disease were Lactobacillus, Corynebacterium, Burkholderiales, and correlation analysis showed that the abundance of coating Fusobacterium was significantly associated with serum high-sensitivity C-reactive protein, IL-6, and IL-8.Hu et al [43] found that synthesis of adult catch-up fat in adult was associated with coating Tannerella forsythia, insulin resistance, high-fat diet, and yellow tongue coating.Lu et al [44] found that the richness and diversity of tongue coating microbiome were significantly increased in the patients with pancreatic head cancer, and abundances of 13 genera (Leptotrichia, Fusobacterium, Rothia, Actinomyces, Corynebacterium, Atopobium, Peptostreptococcus, Catonella, Oribacterium, Filifactor, Campylobacter, Mortierella and Tannerella) were oberved to be significantly increased.Among them, Haemophilus, Porphyromonas, Ciliates and Fusobacterium owned potential diagnostic value for pancreatic head cancer.Wu et al [45] found that the increased abundance of coating Streptococcus was significantly associated with the GC risk.Han et al [46] and Hu et al [47] found that the tongue coating was thicker in the GC patients and colorectal cancer patients than that in the healthy controls, and the richness and diversity of microbiome were significantly decreased in the patients' tongue coating.Wang et al [48] found that the patients with chronic atrophic gastritis had significantly increased bacterial genera, such as Cilia, Veillon, Rossella, Prevobacterium, Stomatobaculum, but had decreased Streptococcus in tongue coating.These studies provided new evidences for oral microbial alternation in prediction of systemic diseases, meanwhile tongue coating microbiome might provide stable, simple and easy noninvasive biomarkers that rivalled the fashionable gut microbiome.

Syndrome differentiation is the key criterion in TCM clinical practice, it is based on the judgement of the experts' experience, but the criterion is still lack of scientificity and applicability.Thus, explorating objective microcosmic biomarkers will provide powerful impetus in the standardization of modern TCM diagnosis.The clinical study on the biology of tongue coating showed that syndromes formation was closely related to the alternation of tongue coatings.For example, Li et al [49] found that Spleen-Stomach Damp-heat syndrome and Qi Deficiency syndrome in the patients with chronic superficial gastritis tended to have a reduced cell maturity index of the tongue coating, and the patients with spleen-stomach damp-heat syndrome had the highest Helicobacter pylori (Hp) infection rate in the patients with chronic superficial gastritis.Lv et al [50] found that the color depth of yellow-greasy coating was negatively related to the apoptotic index of tongue coating cells but was positively related to bacterial abundance in the damp-heat syndrome.Based on the high-throughput sequencing of tongue coating microbiome, Wang et al [51] found that, chronic heart failure patients with the syndrome (Qi-yang Deficiency, Bloodstasis, Water-stagnation syndrome, and Qi-yin Deficiency Blood-stasis, Water-stagnation) had increased coating Neisseria and two decreased genera (Prevotella, Veillonella).Compared with the syndrome of Qi-yin Deficiency and Bloodstasis, the coating abundance of Streptococcus decreased, while the coating abundance of Fusobacterium increased in patients with Qiyang Deficiency and Blood-stasis syndrome.Luo et al [52] found that the Hyperactivity of Liver-fire syndrome in the blood hypertensive patients manifested as bitterness, halitosis, dry mouth and toothache.The richness of the coating microbiome (observed OTUs) was significantly increased, and relative abundances of the genus Streptococcus, Rosella, Neisser and Sphingomonas were significantly increased.These above results indicated that tongue coating microbiome may provide unique microscopic diagnostic markers in the diseasesyndrome discrimination.

To investigate the stability of tongue coating microbiome, seven periodontal pathogenic bacteria could be detected before and after tongue cleaning, i.e.Prevotella intermedia, Prevotella nigrescens, Streptococcus constellatus, Tannerella forsythia, Porphyromonas gingivalis, Treponema denticola, and Prevotella melaninogenica [53].Tanner et al [54] found that several periodontal pathogens, such as Porphyromonas gingivalis and Tannerella forsythia, were observed to be increasing on the tongue coating with age, and their detecting sensibity in the tongue coating was higher than that in the plaque [55].Thus, tongue coating microbiome showed the characteristic stability and might be the potential reservoir of periodontal disease.

Halitosis, a common oral symptom, refers to the bad odor emitted by the mouth during breathing and has long been plaguing in the common life.Thus, halitosis is concerned both in modern medicine and in TCM.The awful stink contains a series of volatile molecules, such as volatile sulphide, propionic acid, butyric acid, cadaverine, putrescine, indole and skatole, which were mostly produced by the oral flora.Because the tongue coating has unique habitat conditions, such as the basal layer of the tongue coating and the saliva covered by the surface contain a lot of nutrients, the surface cracks and wrinkles of the tongue coating can form a good micro-oxygen environment and become the main gathering place of the oral flora.Researchers had found that brushing tongue dorsum might control the generation of tongue coating, and combined application of antibacterial drugs to reduce the tongue coating microbiome ccoul effectively relieve halitosis [56].Bacterial richness of tongue coating in children with halitosis was significantly higher than that in healthy controls, and the significantly increased Leptotrichia wadei and Peptostreptococcus stomatis were related to children's halitosis.Further metagenomic analysis showed that oral flora of children with halitosis was enriched with hydrogen sulfide-related metabolic pathways and symbiotic relationship of the tongue-toating flora is more complicated than the that of saliva [57].Seerangaiyan et al [58] also found that Aggregatibacter, Campylobacter, Capnocytophaga, Clostridiales, Dialister, Leptotrichia, Parvimonas, Peptostreptococcus, Peptocococcus, Prevotobacter, Selenomonas, Tannerella and Treponema were the tongue coating markers of halitosis patients.Evidencebased TCM researches found that the main syndromes of halitosis patients included Spleen-Stomach Damp-heat, Damp-heat Intrinsic syndrome, Blazing Stomach Fire syndrome, Gastrointestinal food Accumulation syndrom，Liver Fire Attacking Stomach syndrom, and Lung Heat syndrom [59].The emergence of halitosis was dominated by Excess Damp Heat and Yin deficiency in TCM clinical practices.Thus, tongue coating flora may be the reasonable entry point for the diagnosis of systemic diseases in combination with traditional Chinese and modern medicine.

4.Potential influencing factors of tongue coating microbiota

TCM believes that everything inside must be outside.Observing the changing of tongue manifestation can help understanding the ups and downs of viscera, blood and disease, and guiding the TCM syndrome differentiation and treatment.Since the different tongue coatings owned different microbial community, the tongue flora may provide potential therapeutic evaluation markers for TCM treatment based on the syndrome differentiation.Zhuo et al [60] used the modification of Huopu Xialing Decoction to treat the patients with Spleen-Stomach damp-heat syndrome, and the yellowgreasy coating was subsided and responding coating flora restored to be like the normal flora, however, the positive control drug (domperidone) could not turned the tongue bacteria to be normal.The results presented the obvious advantages of TCM treatment guiding by the overall view.Lu et al [61] found that Jianpi Shenshi Decoction had a recovery effect on the microbiota both in the gut and the tongue coating in the patients with Spleen deficiency, dampness-diarrhea syndrome, suggesting that the gut flora be related to the tongue coating microbiota.Sun et al [62] used Xinkai Kuijiang method to eあectively treat the upper gastrointestinal precancerous lesions, and promoted the abundances of Granulicatella, Gemella and Haemophilus in tongue coating.These studies suggested that tongue coating microbiota can provide potential biomarkers for TCM therapeutic methods and prescriptions.

Epidemiological studies had shown that poor oral health was an important risk factor for chronic systemic diseases such as cardiovascular disease [63], diabetes [64] and malignant tumors [65].Improving oral hygiene is an important preventive measure to prevent the systemic diseases.Sreenivasan et al [66] found that chlorhexidine mouthwash could reduce the abundance of bacteria in the tongue coating and saliva.In particular, the effects on anaerobes, gram-positive bacteria and gramnegative bacteria were consistent with those on hydrogen sulfide/proteolytic enzymeproducing odor-producing bacteria.Asakawa et al [67] investigated the coating microbiota in the community elderly population, and cluster analysis presented two distinct clusters, in which the cluster composing of Prevotella histicola, Veillonella atypica, Streptococcus salivarius and Streptococcus parasanguinis were associated with increasing mortality of pneumonia.Furthermore, the older adults with dentures had much higher density of fungi, suggesting that older adults with poor oral health might swallow more harmful oral microbiota.Mugita et al [68] proposed that the oral cavity be the microbial harbour for respiratory tract infection in the elderly, and found that the oral administration of protease tablets could remove the tongue coating in the elderly.The further experiment confirmed that the papain and trypsin could inhibit the formation of oral biofilms in vitro.The results indicated that the tongue coating microbiota play a key role in the maintenance of oral hygiene and proved once again thata the tongue coating was the shelter of oral microbiome.Nakano et al [69] studied the eあects of salivary antibacterial proteins (lactoferrin and lactoperoxidase) on plaque and tongue microbiota and found that the total relative abundances of Gram-negative bacteria decreased in the plaque and tongue coating, which was also related to the alleviation of plaque and tongue coating.The above results suggested that the variation of tongue coating microbiome be used as potential criteria for evaluating oral hygiene and health status.

In addition, the TCM theory of "Three Considerations and Measures" insists that the TCM clinical practice pay attention on the real environment, space-time and human emotions guiding by the holistiv view.Here presumed that the tongue coating microbiome be an interesting entry point to explore the scientific connotation of the theory.For example, Sun et al [70] found that there was an obvious correlation between tongue coating and soil bacteria in the patients with gastrointestinal precancerous lesions in Yangzhong area, and there was a significant positive correlation between the relative abundances of four bacterial genera (Capnocytophaga, Streptobacillus, Actinomyces and Haemophilus).Previous studies showed that the gut microbioata could be influenced by many factors, such as age, gender, geography, heredity, diet, etc [71-74].However, it is still unclear that whether the tongue coating microbiome be affected by these factors.Because of the close linkage of microbiome along the entire digestive tract inluding the tongue coating and intestine, here proposed that the tongue coating microbiota be as stable and plastic as the intestinal microbiota [75], and can be a breakthrough point in explorating the scientific significance of TCM "Three Considerations and Measures" theory, and will provide a new idea to interpret the TCM holistic view.

Discussion

With the rapid development of modern medicine, the limitations become more and more obvious, for example, over-detailed specialties and the fragmentation of knowledge obstructed complementary advantages of modern medicine and traditional medicine.And many scholars had put forward the concept of integrated medicine.TCM thoery persists in the characteristics of holistic view and is still acting as an important part of traditional medicine in the world.Thus, the combination of Chinese and modern medicine is conducive for the further understanding of human body via the analytical and comprehensive means guided by TCM theory [76].Where is the way for integrated medicine going? Tongue diagnosis is the most easy, objective and simple method for all the clinicians and masses, and TCM thinks that tongue has intercommunication with the viscera by the main and collateral channels.The TCM clinical practice accumulated a lot of unique experiences, which may provide a rational interpret for the linkage between tongue coating microbiota and prevention, diagnosis, therapy of the diseases.Thus, tongue coating microbiota could be a reasonable breakthrough point for the integrating medical research, which will provide potiental biomarkers for diagnosis, treatment and prognosis of holistic integrative medicine, and blaze a trail in the developmen of both mordern medicine and Chinese medicine.