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MIRA SYAHIRA RHYME 43387632 23 SEPTEMBER 2016 BENCH D MICR3004

Classification

Higher order taxa

Bacteria –Terrabacteria group- Actinobacteria- Actinobacteria- Micrococcales – Micrococcaceae – Rothia [1]

Species

Rothia dentocariosa. The types of strains: ATCC 17931 , ATCC 29070 , BCRC 12926, CCM 3472 , CCM 7007 , CCRC 12926 , CCUG 15599 , CCUG 35437 , CDC X599 , CIP 81.63 , CIP 81.63T , CIP 81.83, CIP 81.83T, CNCTC 5686, DSM 20352, DSM 43762 , DSM 46363 , G.D. Roth XDIA , GTC 267 , HNCMB 110019, IAM 14816 , IFM 1284 , IFO 12531 , IMET 11515 , IMSNU 21309, JCM 3067, K21 , KCC A-0067 , KCTC 3204 , KCTC 3577, Kloos K21 , LMG 21025 , NBRC 12531, NCDC W-858, NCTC 10917 , NCTC 12102 , NRRL B-14758, NRRL B-8017 , PCM 2349 , Roguinsky K21 , Roth XDIA ,W.E. Kloos K 21, XD-1A , XDIA

Description and significance

Rothia dentocariosa (R. dentocariosa) was initially isolated from dental plaque and caries by Onishi in 1949 [7]. It belongs to the genus Rothia and family Micrococcaceae, which was previously thought to belong to the family Actinomycetaceae [1, 2, 5]. This genus Rothia has faced a number of taxonomic changes for the last 15 years [3]. This species of Rothia is commonly found in human oropharynx, upper respiratory tract and mouth [8]. R. dentocariosa is a non-acid fast, non-spore-forming, non-motile and non-pigmented gram positive bacteria [4]. This pleomorphic bacteria can be in either in coccoid to rod-shaped or filamentous form in anaerobic condition. The morphology varies in different culture type such that the filamentous and coccoid forms are more commonly seen in plates and fluid respectively [4].The cells can form single, paired and clustered or chained and colonial structures that are either smooth, convex type or rough form depending on cells maturity [4, 6]. R. dentocariosa prefers aerobic condition such that it would grow faster and does not require carbon dioxide or lipids for growth [4]. This facultative anaerobe bacteria was initially thought to be non-pathogenic until a case involving peri-appendiceal abscess was reported in 1975 [11]. R. dentocariosa was also found to cause other form of abscess, opportunistic pneumonia infection and predominantly endocarditis in which patients are also associated with valvular heart disease, carious teeth and periodontal disease [4, 7, 9]. Other complications resulting from endocarditis include periocoronitis, endophtalmitis, septic arthritis, bacteremia, cornel ulcer, arteriovenous fistula and intracerebral haemorrhage [3, 9]. More recently, R. dentocariosa has been associated with intrauterine foetal death [10].Hence, it is important to study this emerging crucial opportunistic pathogenic bacteria as it is present as normal oral flora that could potentially impact humans’ health.

Genome structure

There are a number of strains that have been associated with R. dentocariosa. Among the strains, strain ATCC 17931 of the bacteria has completed genome assembly and gene annotation (ENSEMBL: ASM16469v2), (GenBank: GCA_000164695.2), (RefSeq: GCF_000164695.2). The total sequence length of the R. dentocariosa genome is 2,506,025 base pair (bp). This particular bacterial strain comprises a total of 1 circular DNA (plasmid) and none assembly gap length [12]. The total number of nucleotides is 2,506,025. The number of protein and RNA genes contained within the genome of this strain are 2,217 and 65 respectively [13]. From the overall gene transcripts which is 2,350, the number of coding genes are 2,217 while the remaining is small non-coding genes [14]. For this specific strain, ATCC 17931, the GC content in terms of moles percentage is 69.7% [15].

Cell structure and metabolism

R. dentocariosa is a gram positive bacteria which results in dark blue-coloured gram staining. Like other gram positive bacteria, this bacteria has thick layer (90% compared to gram negative) of peptidoglycan embedded with teichoic acid and lipoteichoic acid. The peptidoglycan layer surrounding the single lipid membrane of the bacteria consists of alanine, glutamic acid and lysine [17]. Polysaccharides that contributes to the cell wall include glucose, galactose, ribose and fructose through the use of both chromatographic and chemical analysis [19]. R. dentocariosa has no mycolic acid on its cellular structure thus making it non-acid fast [4]. Furthermore, this cocci to rod and sometimes filamentous shaped bacteria has no flagellar and is non motile [4]. Rothia spp. including R. dentocariosa utilise their capability of biofilm formation activity in further infecting their hosts. Gram positive cocci bacteria like R. dentocariosa usually forms the conditioning layer of the biofilm forming on tooth surfaces and gingivae [18]. These biofilms forming on oral surfaces allow them to develop resistance to antibiotics better than planktonic cells. However, multiple reports have shown that nanoparticles (NPs), the alternatives to traditional antimicrobial agents, have the promising antimicrobial and antibiofilm activities against pathogenic bacteria [16]. R. dentocariosa has well studied metabolic pathways which include energy metabolism comprising of carbon fixation, nitrogen, sulfur and methane. Other major metabolisms are carbohydrate and lipid, nucleic acid and secondary metabolism which consists of aromatics degradation and the biosynthesis of secondary metabolite such as monolignol, flavanone, flavonoid and paspaline. This bacteria has incomplete TCA (citrate) cycle and almost complete functioning of Complex III of respiratory chain thus categorizing it as having atypical respiration [20]. This bacteria is considered fermentative that produces lactic acid and acetic acid major product for glucose fermentation [4].

Ecology

R. dentocariosa is as previously mentioned, a facultative anaerobe which grows better in aerobic condition [4]. This bacteria usually inhabits human host’s throat and mouth specifically dental caries [8]. It also forms biofilm on gingivae together with other colonizing bacteria that predominantly comprises of gram positive cocci bacteria [18]. The highly diverse oral microbiome comprises of biofilms of different types, compositional and habitats within the oral cavity such either both dental and mucosal or just the teeth, which is preferred by R. dentocariosa [21].

Pathology

Infections related to R. dentocariosa comprises mainly of periodontal disease. Severe pericoronitis can also occur and allows the isolation of the bacteria from pericoronal pockets of mandibular third molars [22]. Another predominant infections related to this bacteria is endocarditis. Although this type of infections is rare, it can be very severe and triggers other complications such as cerebral and perivalvular abscess, abdominal aneurysm, vertebral osteomyelitis [24] and intracerebral haemorrhage [3, 23]. Subsequent to endocarditis due to R. dentocariosa infection other clinical manifestations include corneal ulcer, septic arthritis, bacterimia, endophtalmitis, peritonitis and abscesses of peri-appendiceal and pilonidal [3]. Studies have also found that this bacteria is associated with opportunistic pulmonary infection in patients with acute myelocytic leukimia [26] and lung cancer [25]. More recently, R. dentocariosa has been associated with intrauterine foetal death [10]. Hence, it can be seen that R. dentocariosa not only cause disease in the oral cavity but also in other important organs in the body. Individuals that are considered listed under the at risk group for Rothia spp. infections comprise of those with (Human immunodeficiency virus) HIV, alcohol issues, immunocompromised, chronic liver disease and diabetes mellitus [26, 27]. Biofilm formation is thought to contribute to the virulence of the bacteria through the development of resistance towards antimicrobial agents [18].

Application to biotechnology

There are two genes within the genome of R. dentocariosa strain ATCC 17931 that are found to be potential drug targets. The two genes are ftsZ and nrdF which encodes for cell division protein FtsZ and Ribonucleotide reductase of class Ib (aerobic) and beta subunit [28]. These two genes are targeted for antibacterial therapy

Current research

Studies have shown that babies of three months age who lacks certain gut bacteria are more prone to develop asthma. Faeces samples collected from a number of babies (subjects) who develop asthma by the age of three were found to be absent of four types of bacteria: Faecalibacterium, Lachnospira, Veillonella and Rothia, or FLVR for short. FLVR is found to facilitate a healthy immune response to fight against asthma. R. dentocariosa was also listed within the Rothia genus that is associated with this condition in babies. The importance of this findings is that children can potentially be treated and prevented from asthma with the administration of probiotics [29].