Dialister invisus

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Dialister invisus sp. By Grace Graham


Higher order taxa

Bacteria – Firmicutes – Clostridia – Clostridiales – Acidaminococcaceae – Dialister- Dialister invisus. E7.25


Dialister invisus, type strain: E7.25

Description and significance

The species D. invisus was first discovered in 2003 by J. Downes and was isolated by 16S rRNA sequencing from root canals of patients with endodontic infections [1]. Six strains of D. invisus E1 E2.20, E3.07, E7.25, E9.48 and E10.39 were identified in all 5 samples of chronic endodontic lesions[1]. D. invisus is recovered mainly from deep periodontal pockets and is found below the gingival margin[1]. Of these strains only one E7.25 has had its genome partially sequenced and constructed[2]. Despite this the metabolic pathways and genes of this strain are still mostly unknown [3]. Culture-independent methods are normally used in identifying D. invisus as culturing this bacteria is very difficult[4]. Culturing of this bacterium has been somewhat successful with the use of Columbia blood agar [5]. After 7 days of incubation at 37oC, in anaerobic conditions, on blood agar, small colonies of D. invisus have developed[1]. Despite the ability to culture this bacterium the recovery of it in mixed anaerobic cultures is difficult[5]. The difficulty in recovering this species from cultures has been linked to its inability to react to biochemical tests and its morphology[3].D. invisus colonies commonly produce a small, circular and transparent morphology [1]. These colonies are made up of non-motile coccobacilli that can occur singly, in pairs, in chains and in small clumps[1]. Gram staining of cultured colonies has shown that this bacterium is gram-negative [3]. Through culturing and locations it has been isolated form this bacteria was concluded to be an asaccharolytic obligately anaerobe.

As D. invisus has been associated with marginal periodontitis, caries, halitosis and apical periodontitis and is commonly isolated from endodontic infections it is consider a significant human pathogen[3]. Understanding the persistent endodontic microbes such as D. invisus can help in determining the best treatment options for individuals with endodontic infections[6]. In order to control or eliminate pathogenic microorganisms associated with endodontic cases a thorough understanding of these pathogens is needed[7].

Genome structure

Little is known about the genomic structure of D. invisus as a complete genome construction has not been conducted. Draft constructions up to the scaffold level have been conducted for the E7.25 strain and have produced some information on the bacteria[2]. The genome size of D. invisus was found to be 1.9 Mb and is contained within one chromosome[2]. There are currently no plasmids apparent from the partial construction of D. invisus but more research would need to be conducted to determine this definitively[2]. Currently 1892 genes in total have been identified for this strain of D. invisus[2]. These genes are organised in the single large chromosome of the bacterium. Of the identified genes 1742 have been recognised as protein coding genes[2]. None of these genes have presently been identified or linked to any specific functions of D. invisus.

Cell structure and metabolism

Information about the cell wall of this bacterium is limited and is largely un-investigated besides its gram-negative status[1]. As D. invisus is considered a non-motile bacteria no extensions of the cell wall such as flagella or pilli are expected to exist[3]. D. invisus has been found in biofilms on dental implants with peri-implantitis[8]. It is unclear whether D. invisus can form biofilms or whether it is just present in biofilms formed by other species, but as it does not seem to possess pilli it is likely that it cannot form biofilms itself[8].

As this bacterium is asaccharolytic it is unable to metabolize carbohydrates and must utilise another form of carbon[3]. The pathway used during metabolism of this bacterium is currently unknown but it is considered to utilize amino acids, peptides, and other non-carbohydrate nutrients for growth[3]. D. invisus is believed to utilise some form of acidogenesis in its metabolic pathway as it is a step in anaerobic digestion[9]. The only known metabolic end products of D. invisus are acetate, lactate and propionate [9]. Acidogensis generally functions through one of three types of fermentation. In the case of D. invisus propionic-type fermentation is believed to occur due to the end products acetate and propionate[10]. Propionic-type fermentation is the most common fermentation in anaerobic microorganisms making it likely that this pathway is utilised in D. invisus [10]. The use of propionic fermentation by D. invisus has not yet been proven but is believed to be possible.


D. invisus is an anaerobe that is most commonly found below the gingival margin and in root canals in people with endodontic infections[3]. The environment of infected root canals is highly favourable to D. invisus as degradation of tissue and inflammatory exudate in patients with apical periodontitis provide amino acids and peptides essential in D. invisus development[3]. The frequent isolation of D. invisus from necrotic root canals supports the conclusion that this environment is conducive to the establishment and growth of D. invisus[3]. Dialister species have also been detected in non-oral human sites. These sites include bacterial vaginosis samples, Fallopian-tube specimens from women with salpingitis, urinary tract infections, intestinal tract, and brain abscess[3]. It is unclear from studies whether D. invisus specifically can be isolated from all these sites but it is highly likely. Other Dialister species such as D. pneumosintes have been found in non-oral sites associated with purulent infections, brain abscesses and bite-wound infections. The capability of this species to exist in non-oral environments, and be associated with disease may indicate that D. invisus may also be able to colonise this environment, as these species are closely related and are believed to share many of the same biological properties[1].D. invisus has also been identified to occur in microbiome gut communities. The bacterium has been identified in both symptomatic and asymptomatic individuals and as such is believed to play some role in the normal microbiome[11]. Due to its presence in the gut D. invisus along with other microbes has been used as an indicator of faecal contamination in rivers[11]. Other then in human samples D. invisus has not yet been isolated from the environment[11].


“D. invisus” appears to be able to be maintained in the body asymptomatically and symptomatically[(11)]. It is unclear as to how this occurs but is believed to be due to the environment in the body in which it is located[(11)]. When found in the intestinal tract “D. invisus” has not be associated with disease[(11)]. When found in the urinary is possibly linked to urinary tract infections[(3)]. When “D. invisus” has been found in the oral cavity it has usually been associated with periocoronitis, marginal and apical periodontitis, caries, halitosis and endodontic infections[(1)]. Specifically the presence of “D. invisus” in root canals has be linked to the formation of apical periodontitis lesions[(3)]. The infection of “D. invisus” and subsequent failure of root canals is due to the persistence and secondary infection capabilities of “D. invisus”[(6)].

The favoured niche for periodontal pathogens is third molar sites in young patients which acts to accommodate these pathogens in otherwise healthy mouths [(4)]. This is known, as bacterial species such as “D. invisus” were recovered in greater incidence from erupted third molars then in other teeth plaque [(4)]. The microbial changes in the oral cavity that indicate the initiation of periodontitis have also been shown to first present in the third molar region of young adults[(4)].

“D. invisus” has also been implicated in bacterial vaginosis and salpingitis when isolated from the female reproductive system[(3)]. As “D. invisus” is further investigated its emergence as a candidate endodontic pathogen has occurred[(3)]. The isolation and culturing of “D. invisus” is believed to be significantly under representing the actual numbers and locations of this species. As culturing this species is difficult it is conceivable that it is located in other areas of the body and has not yet been found.

As “D. invisus” has been associated with disease studies of its status in antibiotic resistance have been conducted. These studies have shown that all Dialister strains are resistant to vancomycin and sensitive to kanamycin and colistin[(5)]. As the association of this bacterium with oral disease intensifies the importance of monitoring the antibiotic resistance evolution of this species increases[(5)].

Application to biotechnology

As there is little to no information about the metabolic processes of “D. invisus” and it does not have any significant physiological abilities that would contribute to bioengineering the use of this species in biotechnology is currently very limited. “D. invisus” has reportedly only been involved in one significant biotechnology avenue. Through the use of this species and many other anaerobic fermenters the metabolic products formic, acetic, propionic, butyric, lactic and valeric acid where produced by acidogenesis of lignocellulosics and liquid effluent[(10)]. Y-alumina was utilised in this process to promote the formation of these acids and simultaneously ethanol[(10)]. The acids and ethanol produced by this reaction was then used for esterification reactions that produced esters[(10)]. The esters produced from this reaction can then be used as a new generation biofuel[(10)]. “D. invisus” has been identified in the mixed bacterial culture that is used in this process. While its importance in this process is unclear it acts as an example of possible industry applications of this bacterium.

Current research

Recent studies of faecal contamination indicators in rivers has identified “D. invisus” as a potential indicator[(12)]. “D. invisus” along with other microorganisms when present together indicate faecal matter. Past use of single indicator studies where highly reliant on the presence of a single microorganism to indicate contamination, which was highly inaccurate. By monitoring for multiple indicators that are specific to humans, the presence of biological waste can more successfully be identified and the source traced[(12)]. Investigations into host-microbial cross-talk in inflammatory bowel diseases has found a link between a reduction in intestinal “D. invisus” and Crohn’s Disease (CD) [(13)]. As the absence/reduction of “D. invisus” has been linked to CD this supports the previously suggested idea that in the intestinal tract “D. invisus” may act as a commensal bacteria[(13)]. Another study into type 2 diabetes may also support the idea that “D. invisus” acts as a commensal bacterial in the intestinal tract. An a-glucosidase inhibitor acarbose has been used effectively to treat and prevent type 2 diabetes. Investigations into the gut microbiome makeup of patients before and after treatment found that acarbose had a positive effect on the growth of Dialister species[(14)]. This species was seen to flourish after the application of this treatment indicating that it may play a role in the prevention of type 2 diabetes onset[(14)].

Other studies of “D. invisus” have mainly focused on its association with disease in the oral cavity. As recently has 2016 a link between “D. invisus” in infected root canals and acute apical abscess has been identified[(7)].


1.http://ijs.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.02640-0#tab2 Downes J, Munson M, Wade WG. 2003. Dialister invisus sp. nov., isolated from the human oral cavity. International Journal of Systematic and Evolutionary Microbiology 53:1937-1940.

2.https://www.ncbi.nlm.nih.gov/genome/?term=txid592028[Organism:noexp]Center WUGS. 2012. Dialister invisus.

3. http://www.sciencedirect.com.ezproxy.library.uq.edu.au/science/article/pii/S0099239906003712Rôças IN, Siqueira JF. 2006. Characterization of Dialister Species in Infected Root Canals. Journal of Endodontics 32:1057-1061.

4. http://www.sciencedirect.com.ezproxy.library.uq.edu.au/science/article/pii/S0278239111016648Mansfield JM, Campbell JH, Bhandari AR, Jesionowski AM, Vickerman MM. 2012. Molecular Analysis of 16S rRNA Genes Identifies Potentially Periodontal Pathogenic Bacteria and Archaea in the Plaque of Partially Erupted Third Molars. Journal of Oral and Maxillofacial Surgery 70:1507-1514.e1506.

5.http://aac.asm.org/content/51/12/4498.full F. Morio HJ-P, L. Dubreuil, E. Jumas-Bilak, L. Calvet, G. Mercier,, R. Devine aHM. 2007. Antimicrobial Susceptibilities and Clinical Sources of Dialister Species▿. Antimicrobial Agents and Chemotherapy 51:4498-4501.

6.Narayanan LL, Vaishnavi C. 2010. Endodontic microbiology. Journal of Conservative Dentistry : JCD 13:233-239.

7.https://www.ncbi.nlm.nih.gov/pubmed/27224567 Letícia M. M. Nóbrega FM, Adriana C. Ribeiro, Márcia A. P. Mayer, Brenda P. F. A. Gomes. 2016. Molecular Identification of Cultivable Bacteria From Infected Root Canals Associated With Acute Apical Abscess. Brazilian Dental Journal 27:644.

8.http://onlinelibrary.wiley.com.ezproxy.library.uq.edu.au/doi/10.1111/clr.12231/full da Silva ES FM, Figueiredo LC, Shibli JA, Ramiro FS, Faveri M. 2014. Microbiological diversity of peri-implantitis biofilm by Sanger sequencing. Clin Oral Implants Res 25:1192-1199.

9.Wade WG. 2015. Dialister, Bergey's Manual of Systematics of Archaea and Bacteria doi:10.1002/9781118960608.gbm00696. John Wiley & Sons, Ltd.

10. http://www.sciencedirect.com.ezproxy.library.uq.edu.au/science/article/pii/S0961953416301507Kandylis P, Bekatorou A, Pissaridi K, Lappa K, Dima A, Kanellaki M, Koutinas AA. 2016. Acidogenesis of cellulosic hydrolysates for new generation biofuels. Biomass and Bioenergy 91:210-216.

11.http://www.pnas.org.ezproxy.library.uq.edu.au/content/111/22/E2329.abstract Eric A. Franzosa XCM, Nicola Segata, Levi Waldron, Joshua Reyes, Ashlee M. Earl, Georgia Giannoukos, Matthew R. Boylan, Dawn Ciulla, Dirk Gevers, Jacques Izard, Wendy S. Garrett, Andrew T. Chan, and Curtis Huttenhower. 2014. Relating the metatranscriptome and metagenome of the human gut. PNAS Plus - Biological Sciences - Microbiology 111:2329-2338.

12.https://link-springer-com.ezproxy.library.uq.edu.au/article/10.1007/s12275-011-0530-6 Ju-Yong Jeong H-DP, Kyong-Hee Lee, Hang-Yeon Weon, Jong-Ok Ka. 2011. Microbial community analysis and identification of alternative host-specific fecal indicators in fecal and river water samples using pyrosequencing. Journal of Microbiology 49:585.

13.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5334117/ Nagao-Kitamoto H, Kamada N. 2017. Host-microbial Cross-talk in Inflammatory Bowel Disease. Immune Network 17:1-12.

14.https://link.springer.com/article/10.1007/s13300-017-0226-y Zhang X, Fang Z, Zhang C, Xia H, Jie Z, Han X, Chen Y, Ji L. 2017. Effects of Acarbose on the Gut Microbiota of Prediabetic Patients: A Randomized, Double-blind, Controlled Crossover Trial. Diabetes Therapy 8:293-307.

This page is written by <Grace Graham> for the MICR3004 course, Semester 2, 2017