Evaluation of the Potential of five Housekeeping Genes for Identification of Quarantine Pseudomonas syringae

The Pseudomonas syringae species, containing approximately 60 pathovars, causes bacterial plant diseases on numerous crops and results in great economic losses. It is difficult to rapidly and accurately identify and detect P. syringae due to its complicated classification system. It has also been shown that housekeeping genes have great potential in phylogenetic analysis and classification of bacteria. In this study, phylogenetic analyses of five housekeeping genes, including 16S rRNA, rpoD, gapA, gltA and gyrB, were performed for 100 Pseudomonas strains. Our results showed that two housekeeping genes (rpoD and gapA) had the maximum ability in distinguishing the majority of Pseudomonas pathovars, whereas rpoD exhibited the best for precise and efficient detection of five P. syringae strains, which is of quarantine significance to China.     

New species of pathogenic Pseudomonas isolated from citrus in Tunisia: Proposal of Pseudomonas kairouanensis sp. nov. and Pseudomonas nabeulensis sp. nov.

A collection of Pseudomonas strains was isolated in different regions of Tunisia in the period 2016–2017 from the fruits and leaves of Citrus sinensis cv. ‘Valencia Late’ and Citrus limon cv. ‘Eureka’ plants with symptoms of blast and black pit disease. A phylogenetic analysis of the housekeeping gene rpoD was used for strain identification at the species level. The results demonstrated the affiliation of these strains with the genus Pseudomonas and revealed the presence of 11 strains representing two putative new species in two monophyletic branches. These strains were analyzed morphologically and genotypically by multilocus sequence analyses of the rpoD, gyrB and 16S rRNA (rrs) gene sequences, and their phenotypic characteristics by API 20NE and Biolog GEN III. Plant pathogenic properties were confirmed on fruits and detached leaves of C. limon cv. ‘Eureka’. Fatty acids and WC MALDI-TOF MS major protein profiles were determined. The genomes of both representatives were sequenced. The average nucleotide index and genome-to-genome distance from KC12^T and E10B^T are below the cut-off established for a described species. These results support the conclusion that the strains KC12^T, KC17, KC20, KC22, KC24A, KC25 and KC26 represent a novel species of Pseudomonas, for which the name of Pseudomonas kairouanensis is proposed. The type strain is KC12^T (=CECT9766 and CFBP 8662). The strains E10B^T, E10AB, E10CB1 and Iy3BA represent another novel species of Pseudomonas for which the name of Pseudomonas nabeulensis is proposed; the type strain is E10B^T (=CECT9765 and CFBP 8661).     

Pseudomonas asturiensis sp. nov., isolated from soybean and weeds

Five strains of gram negative bacteria, isolated from soybean (LPPA 221^T, 222 and 223) and weeds (LPPA 816 and 1442), were analyzed by a polyphasic approach. The isolates showed variation in their phenotypic traits and were placed in the Pseudomonas fluorescens lineage, based on 16S rRNA gene sequence phylogeny, as a single but well separated cluster. MLSA analysis based on gyrB and rpoD sequences clustered the strains in a single branch in the Pseudomonas syringae group, and revealed P. viridiflava as closest relative. DNA–DNA hybridizations showed medium levels of DNA–DNA relatedness with the type strain of P. viridiflava (50%) and lower levels (<32%) with other type strains of the P. syringae group, supporting classification within a novel species of the genus Pseudomonas. The strains can be distinguished from species of the P. syringae group by the fatty acid C_17:0 cyclo that is present in a low amount (2.5%) and from P. viridiflava by their inability to assimilate d-tartrate and d-sorbitol, and by the formation of red colonies on TTC medium. For this new species, the name Pseudomonas asturiensis sp. nov. is proposed. The type strain is LPPA 221^T (=LMG 26898^T = CECT 8095^T).     

Pseudomonas soli sp. nov., a novel producer of xantholysin congeners

A chemoorganotrophic Gram-negative bacterium was isolated by means of a diffusion sandwich system from a soil sample from the Sierra Nevada National Park, Spain. Strain F-279,208^T was oxidase and catalase positive, strictly aerobic, non-spore-forming and motile by single polar flagellum. Phylogenetic analysis of the 16S rRNA, gyrB, rpoB and rpoD genes revealed that strain F-279,208^T belongs to the Pseudomonas putida group with Pseudomonas mosselii and Pseudomonas entomophila as its closest relatives. DNA–DNA hybridization assays and phenotypic traits confirmed that this strain belongs to a novel species of the genus Pseudomonas, for which the name Pseudomonas soli sp. nov. is proposed. The type strain is F-279,208^T (=DSM 28043^T = LMG 27941^T), and during fermentation it produces xantholysins, a family of lipodepsipeptides. The major compound, xantholysin A, showed an interesting activity in a RCC4 kidney tumor cell line with inactivation of VHL linked with the HIF pathway, without any cytotoxic effects against other human tumor cell lines tested including, liver, pancreas and breast.     

Pseudomonas laurylsulfatovorans sp. nov., sodium dodecyl sulfate degrading bacteria,isolated from the peaty soil of a wastewater treatment plant

Pseudomonas are known from their flexible degradation capabilities and their engagement in xenobiotic biotransformation and bioremediation in habitats like soil, active sludge, plant surfaces, and freshwater or marine environments. Here we present taxonomic characterization of three efficient sodium dodecyl sulfate degrading strains: AP3_10, AP3_20 and AP3_22^T belonging to the genus Pseudomonas, recently isolated from peaty soil used in a biological wastewater treatment plant. Sequence analyses of 16S rRNA and housekeeping genes: gyrB, rpoD and rpoB showed that the three closely related isolates classify within the Pseudomonas jessenii subgroup. ANIb or dDDH genomic comparisons of AP3_22^T (type strain DSM 105098^T = PCM 2904^T) supported by biochemical tests showed that the isolates differ significantly from their closest relatives. The combined genotypic, phenotypic and chemotaxonomic data strongly support the classification of the three strains: AP3_10, AP3_20 and AP3_22^T as a novel species of Pseudomonas, for which we propose the name Pseudomonas laurylsulfatovorans sp. nov. with AP3_22^T as the type strain.     

<Emphasis Type="Italic">Beauveria bassiana</Emphasis> pathogenicity to the cherry slugworm, <Emphasis Type="Italic">Caliroa cerasi</Emphasis> (Hymenoptera: Tenthredinidae) larvae

The cherry slugworm Caliroa cerasi is a significant destructive pest of sour cherries (Prunus cerasus) in Turkey. The potential of entomopathogenic fungi for controlling C. cerasi was evaluated. The effects of exposure methods and conidial concentrations (1 × 10⁶, 1.5 × 10⁶, 1 × 10⁷ and 1.5 × 10⁷ conidia/ml) on mature larvae of C. cerasi infected by Beauveria bassiana were investigated under laboratory conditions. Larvae sprayed directly with B. bassiana conidial suspensions and larvae exposed to B. bassiana-treated leaves resulted in 100% mortality within 2.90 and 2.77 days, respectively. The median lethal time (LT₅₀) and days to mortality were highest in the 1.0 × 10⁷ concentrations of conidia for both direct spray and leaf exposure. The present study suggests that B. bassiana has good potential for control of the cherry slugworm, C. cerasi.     

Pseudomonas versuta sp. nov., isolated from Antarctic soil

In this study we analysed three bacterial strains coded L10.10^T, A4R1.5 and A4R1.12, isolated in the course of a study of quorum-quenching bacteria occurring in Antarctic soil. The 16S rRNA gene sequence was identical in the three strains and showed 99.7% pairwise similarity with respect to the closest related species Pseudomonas weihenstephanensis WS4993^T. Therefore, the three strains were classified within the genus Pseudomonas. Analysis of housekeeping genes (rpoB, rpoD and gyrB) sequences showed similarities of 84-95% with respect to the closest related species of Pseudomonas, confirming its phylogenetic affiliation. The ANI values were less than 86% to the closest related species type strains. The respiratory quinone is Q9. The major fatty acids are C16:0, C16:1 ω7c/ C16:1 ω6c in summed feature 3 and C18:1 ω7c / C18:1 ω6c in summed feature 8. The strains are oxidase- and catalase-positive. Growth occurs at 4–30 °C, and at pH 4.0–10. The DNA G+C content is 58.2–58.3 mol %. The combined genotypic, phenotypic and chemotaxonomic data support the classification of strains L10.10^T, A4R1.5 and A4R1.12 into a novel species of Pseudomonas, for which the name P. versuta sp. nov. is proposed. The type strain is L10.10^T (LMG 29628^T, DSM 101070^T).     

Pseudomonas sivasensis sp. nov. isolated from farm fisheries in Turkey

A study of 91 isolates from fish farms in Turkey showed that isolates P7^T, P11, P24b, P29, P72, P73 and P158 belonged to the genus Pseudomonas according to 16S rRNA nucleotide sequence analysis. The analysis of the sequences of the RNA polymerase sigma factor gene (rpoD) located these strains in the Pseudomonas fluorescens lineage of species within the P. fluorescens subgroup, close to the cluster composed of the species Pseudomonas grimontii, Pseudomonas marginalis and Pseudomonas panacis. Based on similarities in the 16S rRNA and rpoD gene sequences of three previously isolated strains from other origins (CCUG 57209, CCUG 62357 and W5.2-93) linked them to the same cluster. A polyphasic taxonomic approach including phenotypic characterization, fatty acid composition, and multilocus sequence analysis, together with whole-cell MALDI-TOF data, corroborated this assumption. The genome G+C mol% contents were 59.48 and 59.71, respectively. The average nucleotide indices based on BLAST analysis and the genome-to-genome distance calculation for the P7^T and CCUG 57209 strains with their closest relative, P. grimontii, were 88.16–88.29% and 38.10–38.20%, respectively. These data confirm that isolates P7^T, P11, P24b, P29, P72, P73, P158, CCUG 57209, CCUG 62357 and W5.2-93 represent a new species for which the name Pseudomonas sivasensis is proposed, with P7^T as a type strain (=CCUG 74260^T= and CECT30107^T).     

Taxonomic description of Pseudomonas rhizovicinus sp. nov., isolated from the rhizosphere of a desert shrub Haloxylon ammodendron

A Gram-negative aerobic bacterium, strain M30-35 ^T, was isolated from the rhizosphere of Haloxylon ammodendron in Tengger desert, Gansu province, northwest China. Our previous research indicated that strain M30-35 ^T can promote the growth of ryegrass (Lolium perenne L.). In this study, strain M30-35 ^T was subjected to a polyphasic taxonomic study. Phylogenetic analysis of the 16S rRNA gene and two other housekeeping genes (gyrB, rpoD) showed that strain M30-35 ^T is a member of Pseudomonas anguilliseptica group. The average nucleotide identity (ANI) scores for strains KMM 3042 ^T and FR1439^T were 76.5% and 83.7%, respectively, and DNA-DNA hybridization (DDH) were 21.6% and 26.6%, respectively, and the rates were less than the threshold range for species determination. The dominant cellular fatty acids of strain M30-35 ^T were C_16:0 (22.7%), summed feature 3 (C_16:1ω7c and/or C_16:1ω6c; 18.5%), summed feature 8 (C_18:1ω7c and/or C_18:1ω6c; 23.1%). The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phospholipid and aminophospholipid and the predominant respiratory quinone was ubiquinone (Q9). On the basis of above data, it can be concluded that strain M30-35 ^T represents a novel species in the genus Pseudomonas, for which the name Pseudomonas rhizovicinus sp. nov. is proposed. The type strain is M30-35 ^T (=?MCCC 1K03247^T?=?KCTC 52664 ^T).

     

Pseudomonas silesiensis sp. nov. strain A3T isolated from a biological pesticide sewage treatment plant and analysis of the complete genome sequence

Microorganisms classified in to the Pseudomonas genus are a ubiquitous bacteria inhabiting variety of environmental niches and have been isolated from soil, sediment, water and different parts of higher organisms (plants and animals). Members of this genus are known for their metabolic versatility and are able to utilize different chemical compounds as a source of carbon, nitrogen or phosphorus, which makes them an interesting microorganism for bioremediation or bio-transformation. Moreover, Pseudomonas sp. has been described as a microorganism that can easily adapt to new environmental conditions due to its resistance to the presence of high concentrations of heavy metals or chemical pollution. Here we present the isolation and analysis of Pseudomonas silesiensis sp. nov. strain A3^T isolated from peaty soil used in a biological wastewater treatment plant exploited by a pesticide packaging company. Phylogenetic MLSA analysis of 4 housekeeping genes (16S rRNA, gyrB, rpoD and rpoB), complete genome sequence comparison (ANIb, Tetranucleotide identity, digital DDH), FAME analysis, and other biochemical tests indicate the A3^T strain (type strain PCM 2856^T = DSM 103370^T) differs significantly from the closest relative species and therefore represents a new species within the Pseudomonas genus. Moreover, bioinformatic analysis of the complete sequenced genome showed that it consists of 6,823,539 bp with a 59.58 mol% G + C content and does not contain any additional plasmids. Genome annotation predicted the presence of 6066 genes, of which 5875 are coding proteins and 96 are RNA genes.     

Pseudomonas aestusnigri sp. nov., isolated from crude oil-contaminated intertidal sand samples after the Prestige oil spill

Strains VGXO14^T and Vi1 were isolated from the Atlantic intertidal shore from Galicia, Spain, after the Prestige oil spill. Both strains were Gram-negative rod-shaped bacteria with one polar inserted flagellum, strictly aerobic, and able to grow at 18–37 °C, pH 6–10 and 2–10% NaCl. A preliminary analysis of the 16S rRNA and the partial rpoD gene sequences indicated that these strains belonged to the Pseudomonas genus but were distinct from any known Pseudomonas species. A polyphasic taxonomic approach including phylogenetic, chemotaxonomic, phenotypic and genotypic data confirmed that the strains belonged to the Pseudomonas pertucinogena group. In a multilocus sequence analysis, the similarity of VGXO14^T and Vi1 to the closest type strain of the group, Pseudomonas pachastrellae, was 90.4%, which was lower than the threshold of 97% established to discriminate species in the Pseudomonas genus. The DNA–DNA hybridisation similarity between strains VGXO14^T and Vi1 was 79.6%, but below 70% with the type strains in the P. pertucinogena group. Therefore, the strains should be classified within the genus Pseudomonas as a novel species, for which the name Pseudomonas aestusnigri is proposed. The type strain is VGXO14^T (=CCUG 64165^T = CECT 8317^T).     

Pseudomonas protegens sp. nov., widespread plant-protecting bacteria producing the biocontrol compounds 2,4-diacetylphloroglucinol and pyoluteorin

Fluorescent Pseudomonas strains producing the antimicrobial secondary metabolite 2,4-diacetylphloroglucinol (Phl) play a prominent role in the biocontrol of plant diseases. A subset of Phl-producing fluorescent Pseudomonas strains, which can additionally synthesize the antimicrobial compound pyoluteorin (Plt), appears to cluster separately from other fluorescent Pseudomonas spp. based on 16S rRNA gene analysis and shares at most 98.4% 16S rRNA gene sequence identity with any other Pseudomonas species. In this study, a polyphasic approach based on molecular and phenotypic methods was used to clarify the taxonomy of representative Phl⁺ Plt⁺ strains isolated from tobacco, cotton or wheat on different continents. Phl⁺ Plt⁺ strains clustered separately from their nearest phylogenetic neighbors (i.e. species from the ‘P. syringae’, ‘P. fluorescens’ and ‘P. chlororaphis’ species complexes) based on rpoB, rpoD or gyrB phylogenies. DNA-DNA hybridization experiments clarified that Phl⁺ Plt⁺ strains formed a tight genomospecies that was distinct from P. syringae, P. fluorescens, or P. chlororaphis type strains. Within Phl⁺ strains, the Phl⁺ Plt⁺ strains were differentiated from other biocontrol fluorescent Pseudomonas strains that produced Phl but not Plt, based on phenotypic and molecular data. Discriminative phenotypic characters were also identified by numerical taxonomic analysis and siderotyping. Altogether, this polyphasic approach supported the conclusion that Phl⁺ Plt⁺ fluorescent Pseudomonas strains belonged to a novel species for which the name Pseudomonas protegens is proposed, with CHA0^T (=CFBP 6595^T, =DSM 19095^T) as the type strain.     

Host specificity,pathogenicity and the presence of virulence genes in Iranian strains of Pseudomonas syringae pv. syringae from different hosts

Pseudomonas syringae pv. syringae (Pss) strains were isolated from almond, apricot, peach, pear, sweet cheery and wheat in Kohgiluye and Boyer-Ahmad, Kordestan, Fras and Chaharmahal and Bakhtiari provinces of Iran. The strains were examined for host specificity, the presence of virulence genes and pathogenicity on different hosts. After inoculation of isolates, in compatible reactions bacterial populations increased within six days of inoculation and final cell numbers increased several-fold over initial inoculum levels, but in incompatible reactions, bacterial populations declined within four days of inoculation. Almond, sweet cherry and wheat isolates induced progressive necrotic symptoms on almond leaves and stems. Apricot, peach and sweet cherry isolates induced necrotic lesions when inoculated on apricot leaves. On pear leaves and stems, only the pear isolate incited pathogenic reaction and isolates from other hosts did not. The syrB gene was detected in all of the tested isolates. Almond and pear isolates did not have the syrD gene. The sypA gene was detected in the almond, peach, pear and sweet cherry isolates while the sypB gene was detected in the apricot, peach, sweet cherry and wheat isolates. Almond, apricot, pear and wheat isolates gave negative results for the detection of nit gene. The gene Ach, was detected only in the peach isolate and gene hrmA, was detected only in the wheat isolate. This study indicates that host specificity exists among different Pss strains, and genes responsible for syringomycin and syringopeptin production contribute to the virulence of Pss strains.     

Pseudomonas gallaeciensis sp. nov., isolated from crude-oil-contaminated intertidal sand samples after the Prestige oil spill

Strains V113^T, V92 and V120 have been isolated from sand samples taken at the Atlantic intertidal shore in Galicia, Spain, after the Prestige oil spill. A preliminary analysis of the 16S rRNA and the partial rpoD gene sequences indicated that these strains belonged to the Pseudomonas genus, but they were distinct from any known Pseudomonas species. They were extensively characterized by a polyphasic taxonomic approach and phylogenetic data that confirmed that these strains belonged to the Pseudomonas pertucinogena group. Phylogenetic analysis of 16S rRNA, gyrB and rpoD gene sequences showed that the three strains were 99% similar and were closely related to members of the P. pertucinogena group, with less than 94% similarity to strains of established species; Pseudomonas pachastrellae was the closest relative. The Average Nucleotide Index based on blast values was 89.0% between V113^T and the P. pachastrellae type strain, below the accepted species level (95%). The predominant cellular fatty acid contents and whole cell protein profiles determined by MALDI-TOF mass spectrometry also differentiated the studied strains from known Pseudomonas species. We therefore conclude that strains V113^T, V92 and V120 represent a novel species of Pseudomonas, for which the name Pseudomonas gallaeciensis is proposed; the type strain is V113^T (= CCUG 67583^T = LMG 29038^T).     

rpoD Gene Pyrosequencing for the Assessment of Pseudomonas Diversity in a Water Sample from the Woluwe River

A water sample from a noncontaminated site at the source of the Woluwe River (Belgium) was analyzed by culture-dependent and -independent methods. Pseudomonas isolates were identified by sequencing and analysis of the rpoD gene. Culture-independent methods consisted of cloning and pyrosequencing of a Pseudomonas rpoD amplicon from total DNA extracted from the same sample and amplified with selective rpoD gene primers. Among a total of 14,540 reads, 6,228 corresponded to Pseudomonas rpoD gene sequences by a BLAST analysis in the NCBI database. The selection criteria for the reads were sequences longer than 400 bp, an average Q₄₀ value greater than 25, and >85% identity with a Pseudomonas species. Of the 6,228 Pseudomonas rpoD sequences, 5,345 sequences met the established criteria for selection. Sequences were clustered by phylogenetic analysis and by use of the QIIME software package. Representative sequences of each cluster were assigned by BLAST analysis to a known Pseudomonas species when the identity with the type strain was greater than or equal to 96%. Twenty-six species distributed among 12 phylogenetic groups or subgroups within the genus were detected by pyrosequencing. Pseudomonas stutzeri, P. moraviensis, and P. simiae were the only cultured species not detected by pyrosequencing. The predominant phylogenetic group within the Pseudomonas genus was the P. fluorescens group, as determined by culture-dependent and -independent analyses. In all analyses, a high number of putative novel phylospecies was found: 10 were identified in the cultured strains and 246 were detected by pyrosequencing, indicating that the diversity of Pseudomonas species has not been fully described.     

Pseudomonas caspiana sp. nov., a citrus pathogen in the Pseudomonas syringae phylogenetic group

In a screening by multilocus sequence analysis of Pseudomonas strains isolated from diverse origins, 4 phylogenetically closely related strains (FBF58, FBF102^T, FBF103, and FBF122) formed a well-defined cluster in the Pseudomonas syringae phylogenetic group. The strains were isolated from citrus orchards in northern Iran with disease symptoms in the leaves and stems and its pathogenicity against citrus plants was demonstrated. The whole genome of the type strain of the proposed new species (FBF102^T = CECT 9164^T = CCUG 69273^T) was sequenced and characterized. Comparative genomics with the 14 known Pseudomonas species type strains of the P. syringae phylogenetic group demonstrated that this strain belonged to a new genomic species, different from the species described thus far. Genome analysis detected genes predicted to be involved in pathogenesis, such as an atypical type 3 secretion system and two type 6 secretion systems, together with effectors and virulence factors. A polyphasic taxonomic characterization demonstrated that the 4 plant pathogenic strains represented a new species, for which the name Pseudomonas caspiana sp. nov. is proposed.     

Pseudomonas prosekii sp. nov., a Novel Psychrotrophic Bacterium from Antarctica

During Czech expeditions at James Ross Island, Antarctica, in the years 2007–2009, the bacterial diversity of the genus Pseudomonas was studied. Twelve fluorescent Pseudomonas strains were isolated from various samples and were subjected to a detailed taxonomic study. A polyphasic approach included genotypic and phenotypic analyses. The genotypic analysis involved sequencing of rrs, rpoB and rpoD genes, DNA–DNA hybridization (DDH) studies as well as manual ribotyping using HindIII endonuclease. The phenotypic characterization included conventional tests as well as biotyping using the Biolog system, protein profiling by SDS-PAGE, and MALDI-TOF MS analysis. Our taxonomic study revealed that all isolates belonged to the same Pseudomonas species with psychrotrophic growth not exceeding 37 °C. The cultures showed a unique position among the phylogenetically related pseudomonads. DDH experiment between the proposed type strain of the antarctic isolates and the closest neighbour P. arsenicoxydans CCM 8423^T showed only 40.9–50.1 % similarity, thus confirming that the characterized strains do not belong to the P. arsenicoxydans species. According to the results obtained we propose the name P. prosekii sp. nov. for this novel Pseudomonas taxon with type strain AN/28/1^T (=CCM 7990^T and LMG 26867^T).     

Bacterial Canker of Sweet Cherry (Prunus avium) in Poland

In Polish climatic conditions cherry cankers resulting from infection by Pseudomonas morsprunorum continue development in summer, but the rate may be slower than in the period from April to June. However, from the well established, active canker developing under the dwarf shoot of the susceptible variety‘Hedelfińska’in July no P. morsprunorum were isolated. On the other hand, numerous strains of the genus Erwinia were found there which caused a hyper sensitivity reaction (HR) on tobacco leaves. From the cracks on the current-year cherry shoots, due to fresh infection and from symptomless leaves P. morsprunorum strains were isolated, always accompanied by those of the Erwinia genus in the approximate proportion 1: 1 or 1:2. The strains of Erwinia genus seemed similar to the DC and YC strains isolated by BILLING and BAKER from pear and apple trees infected by fireblight and also to the strains in group III of the bacteria isolated by CROSSE from cherry leaves. In two tests (immediately after isolation and after 4 months of storage) the strains of the Erwinia genus and 3 nonidentified isolates induced HR. At a third test, after 10 months of preservation these strains were HR-negative in contrast to the P. morsprunorum isolates. The fact that strains of the Erwinia genus inducing HR were isolated in large numbers from active cherry canker where pathogenic bacteria were not detected, may indicate that they play some role in the development of cherry tree canker.     

Streptococcus panodentis sp. nov. from the oral cavities of chimpanzees

Three strains TKU9, TKU49 and TKU50^T, were isolated from the oral cavities of chimpanzees (Pan troglodytes). The isolates were all gram‐positive, facultative anaerobic cocci that lacked catalase activity. Analysis of partial 16S rRNA gene sequences showed that the most closely related species was Streptococcus infantis (96.7%). The next most closely related species to the isolates were S. rubneri, S. mitis, S. peroris and S. australis (96.6 to 96.4%). Based on the rpoB and gyrB gene sequences, TKU50^T was clustered with other member of the mitis group. Enzyme activity and sugar fermentation patterns differentiated this novel bacterium from other members of the mitis group streptococci. The DNA G + C content of strain TKU50^T was 46.7 mol%, which is the highest reported value for members of the mitis group (40–46 mol%). On the basis of the phenotypic characterization, partial 16S rRNA gene and sequences data for two housekeeping gene (gyrB and rpoB), we propose a novel taxa, S. panodentis for TKU 50^T (type strain = CM 30579^T = DSM 29921^T), for these newly described isolates.