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  1. Selective isolation and characterisation of novel members of the family Nocardiopsaceae and other actinobacteria from a marine sediment of Tioman Island
    Ng ZY, Tan GYA
    Antonie Van Leeuwenhoek, 2018 May;111(5):727-742.
    PMID: 29511956 DOI: 10.1007/s10482-018-1042-8
    Tioman Island is one of many sources for underexplored actinobacterial diversity in Malaysia. Selective isolation, molecular profiling, 16S rRNA gene sequencing and phylogenetic analyses were carried out to highlight the diversity of the marine actinobacterial community in a sediment collected off Tioman Island. A high number of diverse actinobacteria were recovered using skim milk/HEPES pre-treatment on a mannitol-based medium. A total of 123 actinobacterial strains were isolated, including thirty obligate marine actinobacteria putatively identified as Salinispora spp. Molecular fingerprinting profiles obtained with a double digestion approach grouped the remaining non-Salinispora-like strains into 24 different clusters, with Streptomyces and Blastococcus as the major clusters. A total of 17 strains were identified as novel actinobacterial species within the genera Streptomyces (n = 6), Blastococcus (n = 5), Marinactinospora (n = 3), Nocardiopsis (n = 1), Agromyces (n = 1) and Nonomuraea (n = 1) based on 16S rRNA gene sequence analyses. Polyphasic data from three putative Marinactinospora spp. showed that the strains represent a new genus in the Nocardiopsaceae family. Crude extracts from the strains were also found to inhibit the growth of Gram-positive (Staphylococcus aureus, Bacillus subtilis) and Gram-negative (Providencia alcalifaciens) pathogens. Hierarchical clustering of the bioactivities of an active fraction revealed a unique profile, which is closely related that of fosfomycin.
  2. Quorum quenching properties of Actinobacteria isolated from Malaysian tropical soils
    Devaraj K, Tan GYA, Chan KG
    Arch Microbiol, 2017 Aug;199(6):897-906.
    PMID: 28364274 DOI: 10.1007/s00203-017-1371-4
    In this study, a total of 147 soil actinobacterial strains were screened for their ability to inhibit response of Chromobacterium violaceum CV026 to short chain N-acyl homoserine lactone (AHL) which is a quorum sensing molecule. Of these, three actinobacterial strains showed positive for violacein inhibition. We further tested these strains for the inhibition of Pseudomonas aeruginosa PAO1 quorum sensing-regulated phenotypes, namely, swarming and pyocyanin production. The three strains were found to inhibit at least one of the quorum sensing-regulated phenotypes of PAO1. Phylogenetic analysis of the 16S rRNA gene sequences indicated that these strains belong to the genera Micromonospora, Rhodococcus and Streptomyces. This is the first report presenting quorum quenching activity by a species of the genus Micromonospora. Our data suggest that Actinobacteria may be a rich source of active compounds that can act against bacterial quorum sensing system.
  3. Amycolatopsis thermophila sp. nov. and Amycolatopsis viridis sp. nov., thermophilic actinomycetes isolated from arid soil
    Zucchi TD, Tan GYA, Goodfellow M
    Int J Syst Evol Microbiol, 2012 Jan;62(Pt 1):168-172.
    PMID: 21378137 DOI: 10.1099/ijs.0.029256-0
    The taxonomic positions of two thermophilic actinomycetes isolated from an arid Australian soil sample were established based on an investigation using a polyphasic taxonomic approach. The organisms had chemical and morphological properties typical of members of the genus Amycolatopsis and formed distinct phyletic lines in the Amycolatopsis methanolica 16S rRNA subclade. The two organisms were distinguished from one another and from the type strains of related species of the genus Amycolatopsis using a range of phenotypic properties. Based on the combined genotypic and phenotypic data, it is proposed that the two isolates be classified in the genus Amycolatopsis as Amycolatopsis thermophila sp. nov. (type strain GY088(T)=NCIMB 14699(T)=NRRL B-24836(T)) and Amycolatopsis viridis sp. nov. (type strain GY115(T)=NCIMB 14700(T)=NRRL B-24837(T)).
  4. Marinitenerispora sediminis gen. nov., sp. nov., a member of the family Nocardiopsaceae isolated from marine sediment
    Ng ZY, Fang BZ, Li WJ, Tan GYA
    Int J Syst Evol Microbiol, 2019 Oct;69(10):3031-3040.
    PMID: 31310190 DOI: 10.1099/ijsem.0.003587
    Three novel actinobacterial strains, designated as TPS16T, TPS81 and TPS83, were isolated from a sample of marine sediment collected from Tioman Island, Malaysia. The strains formed abundant branched substrate mycelia without fragmentation along with production of blue spores and blue diffusible pigment on soybean meal agar. The strains could grow at pH ranging from pH 6 to 12 and in 0-8 % (w/v) NaCl. Cell-wall hydrolysis showed the presence of meso-diaminopimelic acid. The strains were closely related to Marinactinospora thermotolerans SCSIO 00652T (97.60 %) and Marinactinospora endophytica YIM 690053T (96.87 %) based on phylogenetic analysis of 16S rRNA gene sequences. Multilocus sequence analysis including gyrB, recA and rpoB genes further confirmed that strain TPS16T represented a distinct branch within the family Nocardiopsaceae. The predominant menaquinones were MK-11(H2), MK-10(H2), MK-11(H4) and MK-10(H4), while the major fatty acids were found to be iso-C16 : 0, anteiso-C17 : 0, iso-C15 : 0 and C18 : 1ω9c. Genome sequencing revealed genome sizes of approximately 6 Mb and G+C contents of 73.8 mol%. A new genus, Marinitenerispora gen. nov., is proposed within the family Nocardiopsaceae based on polyphasic data and the type species is Marinitenerispora sediminis gen. nov., sp. nov. The type strain is TPS16T (=DSM 46825T=TBRC 5138T).
  5. Taxonomic note on the family Pseudonocardiaceae based on phylogenomic analysis and descriptions of Allosaccharopolyspora gen. nov. and Halosaccharopolyspora gen. nov
    Teo WFA, Tan GYA, Li WJ
    Int J Syst Evol Microbiol, 2021 Oct;71(10).
    PMID: 34714227 DOI: 10.1099/ijsem.0.005075
    The taxonomic positions of members within the family Pseudonocardiaceae were assessed based on phylogenomic trees reconstructed using core-proteome and genome blast distance phylogeny approaches. The closely clustered genome sequences from the type strains of validly published names within the family Pseudonocardiaceae were analysed using overall genome-related indices based on average nucleotide identity, average amino acid identity and digital DNA-DNA hybridization values. The family Pseudonocardiaceae consists of the type genus Pseudonocardia, as well as the genera Actinoalloteichus, Actinocrispum, Actinokineospora, Actinomycetospora, Actinophytocola, Actinopolyspora, Actinorectispora, Actinosynnema, Allokutzneria, Allosaccharopolyspora gen. nov., Amycolatopsis, Bounagaea, Crossiella, Gandjariella, Goodfellowiella, Haloactinomyces, Haloechinothrix, Halopolyspora, Halosaccharopolyspora gen. nov., Herbihabitans, Kibdelosporangium, Kutzneria, Labedaea, Lentzea, Longimycelium, Prauserella, Saccharomonospora, Saccharopolyspora, Saccharothrix, Salinifilum, Sciscionella, Streptoalloteichus, Tamaricihabitans, Thermocrispum, Thermotunica and Umezawaea. The G+C contents of the Pseudonocardiaceae genomes ranged from 66.2 to 74.6 mol% and genome sizes ranged from 3.69 to 12.28 Mbp. Based on the results of phylogenomic analysis, the names Allosaccharopolyspora coralli comb. nov., Halosaccharopolyspora lacisalsi comb. nov. and Actinoalloteichus caeruleus comb. nov. are proposed. This study revealed that Actinokineospora mzabensis is a heterotypic synonym of Actinokineospora spheciospongiae, Lentzea deserti is a heterotypic synonym of Lentzea atacamensis, Prauserella endophytica is a heterotypic synonym of Prauserella coralliicola, and Prauserella flava and Prauserella sediminis are heterotypic synonyms of Prauserella salsuginis. This study addresses the nomenclature conundrums of Actinoalloteichus cyanogriseus and Streptomyces caeruleus as well as Micropolyspora internatus and Saccharomonospora viridis.
  6. Devosia elaeis sp. nov., isolated from oil palm rhizospheric soil
    Mohd Nor MN, Sabaratnam V, Tan GYA
    Int J Syst Evol Microbiol, 2017 Apr;67(4):851-855.
    PMID: 27902276 DOI: 10.1099/ijsem.0.001683
    A bacterial isolate, designated strain S37T, was isolated from the rhizosphere of oil palm (Elaeis guineensis). Strain S37T was found to be Gram-stain-negative, aerobic, motile and rod shaped. Based on 16S rRNA gene sequence analysis, strain S37T was most closely related to Devosia albogilva IPL15T (97.3 %), Devosia chinhatensis IPL18T (96.8 %) and Devosia subaequoris HST3-14T (96.5 %). The G+C content of the genomic DNA was 63.0 mol%, and dominant cellular fatty acids were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), 11-methyl C18 : 1ω7c and C16 : 0. The predominant isoprenoid quinone was ubiquinone-10 (Q-10), and the major polar lipids were phosphatidylglycerol, diphosphatidylglycerol, glycolipid and phospholipids. Based on the polyphasic taxonomic data, it is clear that strain S37T represents a novel species of the genus Devosia within the family Hyphomicrobiaceae, for which we propose the name Devosia elaeis sp. nov., with strain S37T (=TBRC 5145T=LMG 29420T) as the type strain.
  7. Streptomyces kebangsaanensis sp. nov., an endophytic actinomycete isolated from an ethnomedicinal plant, which produces phenazine-1-carboxylic acid
    Sarmin NIM, Tan GYA, Franco CMM, Edrada-Ebel R, Latip J, Zin NM
    Int J Syst Evol Microbiol, 2013 Oct;63(Pt 10):3733-3738.
    PMID: 23645019 DOI: 10.1099/ijs.0.047878-0
    A spore-forming streptomycete designated strain SUK12(T) was isolated from a Malaysian ethnomedicinal plant. Its taxonomic position, established using a polyphasic approach, indicates that it is a novel species of the genus Streptomyces. Morphological and chemical characteristics of the strain were consistent with those of members of the genus Streptomyces. Analysis of the almost complete 16S rRNA gene sequence placed strain SUK12(T) in the genus Streptomyces where it formed a distinct phyletic line with recognized species of this genus. The strain exhibited highest sequence similarity to Streptomyces corchorusii DSM 40340(T) (98.2 %) followed by Streptomyces chrestomyceticus NRRL B-3310(T) (98.1 %). The G+C content of the genomic DNA was 74 mol%. Chemotaxonomic data [MK-9(H8) as the major menaquinone; LL-diaminopimelic acid as a component of cell-wall peptidoglycan; C12 : 0, C14 : 0, C15 : 0 and C17 : 1 as the major fatty acids; phospholipid type II] supported the affiliation of strain SUK12(T) to the genus Streptomyces. The results of the phylogenetic analysis and phenotypic data derived from this and previous studies allowed the genotypic and phenotypic differentiation of strain SUK12(T) from the related species of the genus Streptomyces. The DNA-DNA relatedness value between strain SUK12(T) and S. corchorusii DSM 40340(T) is 18.85±4.55 %. Strain SUK12(T) produces phenazine-1-carboxylic acid, known as tubermycin B, an antibacterial agent. It is proposed, therefore, that strain SUK12(T) ( = DSM 42048(T) = NRRL B-24860(T)) be classified in the genus Streptomyces as the type strain of Streptomyces kebangsaanensis sp. nov.
  8. Amycolatopsis nigrescens sp. nov., an actinomycete isolated from a Roman catacomb
    Groth I, Tan GYA, González JM, Laiz L, Carlsohn MR, Schütze B, et al.
    Int J Syst Evol Microbiol, 2007 Mar;57(Pt 3):513-519.
    PMID: 17329776 DOI: 10.1099/ijs.0.64602-0
    The taxonomic status of two actinomycetes isolated from the wall of a hypogean Roman catacomb was established based on a polyphasic investigation. The organisms were found to have chemical and morphological markers typical of members of the genus Amycolatopsis. They also shared a range of chemical, molecular and phenotypic markers which served to separate them from representatives of recognized Amycolatopsis species. The new isolates formed a branch in the Amycolatopsis 16S rRNA gene sequence tree with Amycolatopsis minnesotensis NRRL B-24435(T), but this association was not supported by a particularly high bootstrap value or by the product of the maximum-parsimony tree-making algorithm. The organisms were distinguished readily from closely related Amycolatopsis species based on a combination of phenotypic properties and from all Amycolatopsis strains by their characteristic menaquinone profiles, in which tetra-hydrogenated menaquinones with 11 isoprene units predominated. The combined genotypic and phenotypic data indicate that the isolates merit recognition as representing a novel species of the genus Amycolatopsis. The name proposed for this novel species is Amycolatopsis nigrescens sp. nov., with type strain CSC17Ta-90(T) (=HKI 0330(T)=DSM 44992(T)=NRRL B-24473(T)).
  9. Emended description of the genus Actinokineospora Hasegawa 1988 and transfer of Amycolatopsis fastidiosa Henssen et al. 1987 as Actinokineospora fastidiosa comb. nov
    Labeda DP, Price NP, Tan GYA, Goodfellow M, Klenk HP
    Int J Syst Evol Microbiol, 2010 Jun;60(Pt 6):1444-1449.
    PMID: 19671714 DOI: 10.1099/ijs.0.016568-0
    The species Amycolatopsis fastidiosa (ex Celmer et al. 1977) Henssen et al. 1987 was proposed, based on morphological and chemotaxonomic observations, for a strain originally described as 'Pseudonocardia fastidiosa' Celmer et al. 1977 in a US patent. In the course of a phylogenetic study of the taxa with validly published names within the suborder Pseudonocardineae based on 16S rRNA gene sequences, it became apparent that this species was misplaced in the genus Amycolatopsis. After careful evaluation of the phylogeny, morphology, chemotaxonomy and physiology of the type strain, it was concluded that this strain represents a species of the genus Actinokineospora that is unable to produce motile spores. The description of the genus Actinokineospora is therefore emended to accommodate species that do not produce motile spores, and it is proposed that Amycolatopsis fastidiosa be transferred to the genus Actinokineospora as Actinokineospora fastidiosa comb. nov. The type strain is NRRL B-16697(T) =ATCC 31181(T) =DSM 43855(T) =JCM 3276(T) =NBRC 14105(T) =VKM Ac-1419(T).
  10. Transcriptional responses of Streptococcus gordonii and Fusobacterium nucleatum to coaggregation
    Mutha NVR, Mohammed WK, Krasnogor N, Tan GYA, Choo SW, Jakubovics NS
    Mol Oral Microbiol, 2018 12;33(6):450-464.
    PMID: 30329223 DOI: 10.1111/omi.12248
    Cell-cell interactions between genetically distinct bacteria, known as coaggregation, are important for the formation of mixed-species biofilms such as dental plaque. Interactions lead to gene regulation in the partner organisms that may be critical for adaptation and survival in mixed-species biofilms. Here, gene regulation responses to coaggregation between Streptococcus gordonii and Fusobacterium nucleatum were studied using dual RNA-Seq. Initially, S. gordonii was shown to coaggregate strongly with F. nucleatum in buffer or human saliva. Using confocal laser scanning microscopy and transmission electron microscopy, cells of different species were shown to be evenly distributed throughout the coaggregate and were closely associated with one another. This distribution was confirmed by serial block face sectioning scanning electron microscopy, which provided high resolution three-dimensional images of coaggregates. Cell-cell sensing responses were analysed 30 minutes after inducing coaggregation in human saliva. By comparison with monocultures, 16 genes were regulated following coaggregation in F. nucleatum whereas 119 genes were regulated in S. gordonii. In both species, genes involved in amino acid and carbohydrate metabolism were strongly affected by coaggregation. In particular, one 8-gene operon in F. nucleatum encoding sialic acid uptake and catabolism was up-regulated 2- to 5-fold following coaggregation. In S. gordonii, a gene cluster encoding functions for phosphotransferase system-mediated uptake of lactose and galactose was down-regulated up to 3-fold in response to coaggregation. The genes identified in this study may play key roles in the development of mixed-species communities and represent potential targets for approaches to control dental plaque accumulation.
  11. Fulltext Revisiting the Taxonomic Status of the Biomedically and Industrially Important Genus Amycolatopsis, Using a Phylogenomic Approach
    Sangal V, Goodfellow M, Blom J, Tan GYA, Klenk HP, Sutcliffe IC
    Front Microbiol, 2018;9:2281.
    PMID: 30319584 DOI: 10.3389/fmicb.2018.02281
    Strains belonging to the genus Amycolatopsis are well known for the production of a number of important antimicrobials and other bioactive molecules. In this study, we have sequenced the genomes of five Amycolatopsis strains including Amycolatopsis circi DSM 45561T, Amycolatopsis palatopharyngis DSM 44832T and Amycolatopsis thermalba NRRL B-24845T. The genome sequences were analyzed with 52 other publically available Amycolatopsis genomes, representing 34 species, and 12 representatives from related genera including Saccharomonospora, Saccharopolyspora, Saccharothrix, Pseudonocardia and Thermobispora. Based on the core genome phylogeny, Amycolatopsis strains were subdivided into four major clades and several singletons. The genus Amycolatopsis is homogeneous with only three strains noted to group with other genera. Amycolatopsis halophila YIM93223T is quite distinct from other Amycolatopsis strains, both phylogenetically and taxonomically, and belongs to a distinct genus. In addition, Amycolatopsis palatopharyngis DSM 44832T and Amycolatopsis marina CGMCC4 3568T grouped in a clade with Saccharomonospora strains and showed similar taxogenomic differences to this genus as well as other Amycolatopsis strains. The study found a number of strains, particularly those identified as Amycolatopsis orientalis, whose incorrect identification could be resolved by taxogenomic analyses. Similarly, some unclassified strains could be assigned with species designations. The genome sequences of some strains that were independently sequenced by different laboratories were almost identical (99-100% average nucleotide and amino acid identities) consistent with them being the same strain, and confirming the reproducibility and robustness of genomic data. These analyses further demonstrate that whole genome sequencing can reliably resolve intra- and, inter-generic structures and should be incorporated into prokaryotic systematics.
  12. Amycolatopsis granulosa sp. nov., Amycolatopsis ruanii sp. nov. and Amycolatopsis thermalba sp. nov., thermophilic actinomycetes isolated from arid soils
    Zucchi TD, Tan GYA, Bonda ANV, Frank S, Kshetrimayum JD, Goodfellow M
    Int J Syst Evol Microbiol, 2012 Jun;62(Pt 6):1245-1251.
    PMID: 21764982 DOI: 10.1099/ijs.0.031039-0
    The taxonomic positions of three thermophilic actinomycetes isolated from arid soil samples were established by using a polyphasic approach. The organisms had chemical and morphological features that were consistent with their classification in the genus Amycolatopsis. 16S rRNA gene sequence data supported the classification of the isolates in the genus Amycolatopsis and showed that they formed distinct branches in the Amycolatopsis methanolica subclade. DNA-DNA relatedness studies between the isolates and their phylogenetic neighbours showed that they belonged to distinct genomic species. The three isolates were readily distinguished from one another and from the type strains of species classified in the A. methanolica subclade based on a combination of phenotypic properties and by genomic fingerprinting. Consequently, it is proposed that the three isolates be classified in the genus Amycolatopsis as representatives of Amycolatopsis granulosa sp. nov. (type strain GY307(T) = NCIMB 14709(T) = NRRL B-24844(T)), Amycolatopsis ruanii sp. nov. (type strain NMG112(T) = NCIMB 14711(T) = NRRL B-24848(T)) and Amycolatopsis thermalba sp. nov. (type strain SF45(T) = NCIMB 14705(T) = NRRL B-24845(T)).
  13. Sciscionella sediminilitoris sp. nov., a Marine Actinomycete Isolated from Cape Rochado, Malaysia, and the Emendations to the Description of the Genus Sciscionella
    Teo WFA, Devaraj K, Nor MNM, Li WJ, Tan GYA
    Curr Microbiol, 2024 Mar 29;81(5):124.
    PMID: 38551738 DOI: 10.1007/s00284-024-03634-8
    In this study, we employed a polyphasic approach to determine the taxonomic position of a newly isolated actinomycete, designated SE31T, obtained from a sediment sample collected at Cape Rochado, Malaysia. Phylogenetic analysis of the 16S rRNA gene sequence revealed that strain SE31T belonged to the family Pseudonocardiaceae and exhibited the highest sequence similarity (98.9%) to Sciscionella marina. Further genomic analysis demonstrated a 93.4% average nucleotide identity and 54.4% digital DNA-DNA hybridization relatedness between strain SE31T and S. marina. The chemotaxonomic characteristics of strain SE31T were typical of the genus Sciscionella, including cell-wall chemotype IV (with meso-diaminopimelic acid as the diagnostic diamino acid, and arabinose and galactose as whole-cell sugars). The identified polar lipids of strain SE31T were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylmethylethanolamine, and hydroxyphosphatidymethylethanolamine. The primary menaquinone observed was MK-9(H4), and the major cellular fatty acid was iso-C16:0. The genomic DNA size of strain SE31T was determined to be 7.4 Mbp with a G+C content of 68.7%. Based on these comprehensive findings, strain SE31T represents a novel species within the genus Sciscionella, in which the name Sciscionella sediminilitoris sp. nov. is proposed. The type strain of Sciscionella sediminilitoris is SE31T (= DSM 46824T = TBRC 5134T).
  14. Fulltext Transcriptional profiling of coaggregation interactions between Streptococcus gordonii and Veillonella parvula by Dual RNA-Seq
    Mutha NVR, Mohammed WK, Krasnogor N, Tan GYA, Wee WY, Li Y, et al.
    Sci Rep, 2019 05 21;9(1):7664.
    PMID: 31113978 DOI: 10.1038/s41598-019-43979-w
    Many oral bacteria form macroscopic clumps known as coaggregates when mixed with a different species. It is thought that these cell-cell interactions are critical for the formation of mixed-species biofilms such as dental plaque. Here, we assessed the impact of coaggregation between two key initial colonizers of dental plaque, Streptococcus gordonii and Veillonella parvula, on gene expression in each partner. These species were shown to coaggregate in buffer or human saliva. To monitor gene regulation, coaggregates were formed in human saliva and, after 30 minutes, whole-transcriptomes were extracted for sequencing and Dual RNA-Seq analysis. In total, 272 genes were regulated in V. parvula, including 39 genes in oxidoreductase processes. In S. gordonii, there was a high degree of inter-sample variation. Nevertheless, 69 genes were identified as potentially regulated by coaggregation, including two phosphotransferase system transporters and several other genes involved in carbohydrate metabolism. Overall, these data indicate that responses of V. parvula to coaggregation with S. gordonii are dominated by oxidative stress-related processes, whereas S. gordonii responses are more focussed on carbohydrate metabolism. We hypothesize that these responses may reflect changes in the local microenvironment in biofilms when S. gordonii or V. parvula immigrate into the system.
  15. Amycolatopsis saalfeldensis sp. nov., a novel actinomycete isolated from a medieval alum slate mine
    Carlsohn MR, Groth I, Tan GYA, Schütze B, Saluz HP, Munder T, et al.
    Int J Syst Evol Microbiol, 2007 Jul;57(Pt 7):1640-1646.
    PMID: 17625209 DOI: 10.1099/ijs.0.64903-0
    Three actinomycetes isolated from the surfaces of rocks in a medieval slate mine were examined in a polyphasic taxonomic study. Chemotaxonomic and morphological characteristics of the isolates were typical of strains of the genus Amycolatopsis. The isolates had identical 16S rRNA gene sequences and formed a distinct phyletic line towards the periphery of the Amycolatopsis mediterranei clade, being most closely related to Amycolatopsis rifamycinica. The organisms shared a wide range of genotypic and phenotypic markers that distinguished them from their closest phylogenetic neighbours. On the basis of these results, a novel species, Amycolatopsis saalfeldensis sp. nov., is proposed. The type strain is HKI 0457(T) (=DSM 44993(T)=NRRL B-24474(T)).
  16. Insecticidal activities of Streptomyces sp. KSF103 ethyl acetate extract against medically important mosquitoes and non-target organisms
    Amelia-Yap ZH, Low VL, Saeung A, Ng FL, Chen CD, Hassandarvish P, et al.
    Sci Rep, 2023 Jan 02;13(1):4.
    PMID: 36593229 DOI: 10.1038/s41598-022-25387-9
    A potentially novel actinobacterium isolated from forest soil, Streptomyces sp. KSF103 was evaluated for its insecticidal effect against several mosquito species namely Aedes aegypti, Aedes albopictus, Anopheles cracens and Culex quinquefasciatus. Mosquito larvae and adults were exposed to various concentrations of the ethyl acetate (EA) extract for 24 h. Considerable mortality was evident after the EA extract treatment for all four important vector mosquitoes. Larvicidal activity of the EA extract resulted in LC50 at 0.045 mg/mL and LC90 at 0.080 mg/mL for Ae. aegypti; LC50 at 0.060 mg/mL and LC90 at 0.247 mg/mL for Ae. albopictus; LC50 at 2.141 mg/mL and LC90 at 6.345 mg/mL for An. cracens; and LC50 at 0.272 mg/mL and LC90 at 0.980 mg/mL for Cx. quinquefasciatus. In adulticidal tests, the EA extract was the most toxic to Ae. albopictus adults (LD50 = 2.445 mg/mL; LD90 = 20.004 mg/mL), followed by An. cracens (LD50 = 5.121 mg/mL; LD90 = 147.854 mg/mL) and then Ae. aegypti (LD50 = 28.873 mg/mL; LD90 = 274.823 mg/mL). Additionally, the EA extract exhibited ovicidal activity against Ae. aegypti (LC50 = 0.715 mg/mL; LC90 = 6.956 mg/mL), Ae. albopictus (LC50 = 0.715 mg/mL; LC90 = 6.956 mg/mL), and An. cracens (LC50 = 0.715 mg/mL; LC90 = 6.956 mg/mL), evaluated up to 168 h post-treatment. It displayed no toxicity on the freshwater microalga Chlorella sp. Beijerinck UMACC 313, marine microalga Chlorella sp. Beijerinck UMACC 258 and the ant Odontoponera denticulata. In conclusion, the EA extract showed promising larvicidal, adulticidal and ovicidal activity against Ae. aegypti, Ae. albopictus, An. cracens, and Cx. quinquefasciatus (larvae only). The results suggest that the EA extract of Streptomyces sp. KSF103 has the potential to be used as an environmental-friendly approach in mosquito control. The current study would serve as an initial step toward complementing microbe-based bioinsecticides for synthetic insecticides against medically important mosquitoes.
  17. Prevalence, Antimicrobial Resistance, and Genetic Diversity of Listeria spp. Isolated from Raw Chicken Meat and Chicken-Related Products in Malaysia
    Chin PS, Ang GY, Yu CY, Tan EL, Tee KK, Yin WF, et al.
    J Food Prot, 2018 Feb;81(2):284-289.
    PMID: 29360399 DOI: 10.4315/0362-028X.JFP-17-186
    Listeria spp. are ubiquitous in nature and can be found in various environmental niches such as soil, sewage, river water, plants, and foods, but the most frequently isolated species are Listeria monocytogenes and Listeria innocua. In this study, the presence of Listeria spp. in raw chicken meat and chicken-related products sold in local markets in Klang Valley, Malaysia was investigated. A total of 44 Listeria strains (42 L. innocua and 2 L. welshimeri) were isolated from 106 samples. Antibiotic susceptibility tests of the L. innocua strains revealed a high prevalence of resistance to clindamycin (92.9%), ceftriaxone (76.2%), ampicillin (73.8%), tetracycline (69%), and penicillin G (66.7%). Overall, 31 L. innocua and 1 L. welshimeri strain were multidrug resistant, i.e., nonsusceptible to at least one antimicrobial agent in three or more antibiotic classes. The majority of the L. innocua strains were placed into five AscI pulsogroups, and overall 26 distinct AscI pulsotypes were identified. The detection of multidrug-resistant Listeria strains from different food sources and locations warrants attention because these strains could serve as reservoirs for antimicrobial resistance genes and may facilitate the spread and emergence of other drug-resistant strains.
  18. Genome characterization and taxonomy of Actinomyces acetigenes sp. nov., and Actinomyces stomatis sp. nov., previously isolated from the human oral cavity
    Tian X, Teo WFA, Wee WY, Yang Y, Ahmed H, Jakubovics NS, et al.
    BMC Genomics, 2023 Dec 04;24(1):734.
    PMID: 38049764 DOI: 10.1186/s12864-023-09831-2
    BACKGROUND: Actinomyces strains are commonly found as part of the normal microflora on human tissue surfaces, including the oropharynx, gastrointestinal tract, and female genital tract. Understanding the diversity and characterization of Actinomyces species is crucial for human health, as they play an important role in dental plaque formation and biofilm-related infections. Two Actinomyces strains ATCC 49340 T and ATCC 51655 T have been utilized in various studies, but their accurate species classification and description remain unresolved.

    RESULTS: To investigate the genomic properties and taxonomic status of these strains, we employed both 16S rRNA Sanger sequencing and whole-genome sequencing using the Illumina HiSeq X Ten platform with PE151 (paired-end) sequencing. Our analyses revealed that the draft genome of Actinomyces acetigenes ATCC 49340 T was 3.27 Mbp with a 68.0% GC content, and Actinomyces stomatis ATCC 51655 T has a genome size of 3.08 Mbp with a 68.1% GC content. Multi-locus (atpA, rpoB, pgi, metG, gltA, gyrA, and core genome SNPs) sequence analysis supported the phylogenetic placement of strains ATCC 51655 T and ATCC 49340 T as independent lineages. Digital DNA-DNA hybridization (dDDH), average nucleotide identity (ANI), and average amino acid identity (AAI) analyses indicated that both strains represented novel Actinomyces species, with values below the threshold for species demarcation (70% dDDH, 95% ANI and AAI). Pangenome analysis identified 5,731 gene clusters with strains ATCC 49340 T and ATCC 51655 T possessing 1,515 and 1,518 unique gene clusters, respectively. Additionally, genomic islands (GIs) prediction uncovered 24 putative GIs in strain ATCC 49340 T and 16 in strain ATCC 51655 T, contributing to their genetic diversity and potential adaptive capabilities. Pathogenicity analysis highlighted the potential human pathogenicity risk associated with both strains, with several virulence-associated factors identified. CRISPR-Cas analysis exposed the presence of CRISPR and Cas genes in both strains, indicating these strains might evolve a robust defense mechanism against them.

    CONCLUSION: This study supports the classification of strains ATCC 49340 T and ATCC 51655 T as novel species within the Actinomyces, in which the name Actinomyces acetigenes sp. nov. (type strain ATCC 49340 T = VPI D163E-3 T = CCUG 34286 T = CCUG 35339 T) and Actinomyces stomatis sp. nov. (type strain ATCC 51655 T = PK606T = CCUG 33930 T) are proposed.

  19. Transcriptomic Responses to Coaggregation between Streptococcus gordonii and Streptococcus oralis
    Choo SW, Mohammed WK, Mutha NVR, Rostami N, Ahmed H, Krasnogor N, et al.
    Appl Environ Microbiol, 2021 10 28;87(22):e0155821.
    PMID: 34469191 DOI: 10.1128/AEM.01558-21
    Cell-cell adhesion between oral bacteria plays a key role in the development of polymicrobial communities such as dental plaque. Oral streptococci such as Streptococcus gordonii and Streptococcus oralis are important early colonizers of dental plaque and bind to a wide range of different oral microorganisms, forming multispecies clumps or "coaggregates." S. gordonii actively responds to coaggregation by regulating gene expression. To further understand these responses, we assessed gene regulation in S. gordonii and S. oralis following coaggregation in 25% human saliva. Coaggregates were formed by mixing, and after 30 min, RNA was extracted for dual transcriptome sequencing (RNA-Seq) analysis. In S. oralis, 18 genes (6 upregulated and 12 downregulated) were regulated by coaggregation. Significantly downregulated genes encoded functions such as amino acid and antibiotic biosynthesis, ribosome, and central carbon metabolism. In total, 28 genes were differentially regulated in Streptococcus gordonii (25 upregulated and 3 downregulated). Many genes associated with transporters and a two-component (NisK/SpaK) regulatory system were upregulated following coaggregation. Our comparative analyses of S. gordonii-S. oralis with different previously published S. gordonii pairings (S. gordonii-Fusobacterium nucleatum and S. gordonii-Veillonella parvula) suggest that the gene regulation is specific to each pairing, and responses do not appear to be conserved. This ability to distinguish between neighboring bacteria may be important for S. gordonii to adapt appropriately during the development of complex biofilms such as dental plaque. IMPORTANCE Dental plaque is responsible for two of the most prevalent diseases in humans, dental caries and periodontitis. Controlling the formation of dental plaque and preventing the transition from oral health to disease requires a detailed understanding of microbial colonization and biofilm development. Streptococci are among the most common colonizers of dental plaque. This study identifies key genes that are regulated when oral streptococci bind to one another, as they do in the early stages of dental plaque formation. We show that specific genes are regulated in two different oral streptococci following the formation of mixed-species aggregates. The specific responses of S. gordonii to coaggregation with S. oralis are different from those to coaggregation with other oral bacteria. Targeting the key genes that are upregulated during interspecies interactions may be a powerful approach to control the development of biofilm and maintain oral health.
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