y2017m01b10 20170130101200 assa nadine@assaf.org.za assa South African Journal of Science S. Afr. J. Sci 1996-7489 01232017 Volume 113 Number 1/2 Antifungal actinomycetes associated with the pine bark beetle, Orthotomicus erosus, in South Africa Zander R. Human Department of Microbiology and Plant Pathology, Forestry and Agriculture Biotechnology Institute, University of Pretoria, Pretoria, South Africa Bernard Slippers http://orcid.org/0000-0003-1491-3858 Department of Genetics, Forestry and Agriculture Biotechnology Institute, University of Pretoria, Pretoria, South Africa Z. Wilhelm de Beer http://orcid.org/0000-0001-9758-8987 Department of Microbiology and Plant Pathology, Forestry and Agriculture Biotechnology Institute, University of Pretoria, Pretoria, South Africa Michael J. Wingfield http://orcid.org/0000-0001-9346-2009 Department of Microbiology and Plant Pathology, Forestry and Agriculture Biotechnology Institute, University of Pretoria, Pretoria, South Africa Stephanus N. Venter http://orcid.org/0000-0002-5726-4918 Department of Microbiology and Plant Pathology, Forestry and Agriculture Biotechnology Institute, University of Pretoria, Pretoria, South Africa Abstract Actinomycete bacteria are often associated with insects that have a mutualistic association with fungi. These bacteria are believed to be important to this insect–fungus association as they produce antibiotics that exclude other saprophytic fungi from the immediate environment. The aim of this study was to investigate the presence of potentially protective actinomycetes associated with Orthotomicus erosus, an alien invasive pine bark beetle, in South Africa. This bark beetle and its relatives have an association with Ophiostomatales species which are often the only fungi found in the bark beetle galleries. We hypothesised that antibiotic-producing actinomycetes could be responsible for the paucity of other fungi in the galleries by producing compounds to which the Ophiostoma spp. are tolerant. Several actinomycetes in the genus Streptomyces and one Gordonia sp. were isolated from the beetle. Interestingly, most isolates were from the same species as actinomycetes associated with other pine-infesting insects from other parts of the world, including bark beetles and the woodwasp Sirex noctilio. Most actinomycetes isolated had strong antifungal properties against the selected test fungi, including Ophiostoma ips, which is the most common fungal symbiont of Orthotomicus erosus. Although the actinomycetes did not benefit Ophiostoma ips and the hypothesis was not supported, their sporadic association with Orthotomicus erosus suggests that they could have some impact on the composition of the fungal communities present in the bark beetle galleries, which is at present poorly understood. 01232017 http://creativecommons.org/licenses/by/2.5/za/ http://creativecommons.org/licenses/by/2.5/za/ 10.17159/sajs.2017/20160215 20170130101200 http://sajs.co.za/antifungal-actinomycetes-associated-pine-bark-beetle-orthotomicus-erosus-south-africa/zander-r-human-bernard-slippers-z-wilhelm-de-beer-michael-j-wingfield-stephanus-n-venter http://sajs.co.za/sites/default/files/publications/pdf/SAJS-113-1-2_de-Beer_ResearchArticle.pdf http://sajs.co.za/sites/default/files/publications/pdf/SAJS-113-1-2_de-Beer_ResearchArticle.pdf http://sajs.co.za/sites/default/files/publications/pdf/SAJS-113-1-2_de-Beer_ResearchArticle.pdf http://sajs.co.za/sites/default/files/publications/pdf/SAJS-113-1-2_de-Beer_ResearchArticle.pdf http://sajs.co.za/sites/default/files/publications/pdf/SAJS-113-1-2_de-Beer_ResearchArticle.pdf http://sajs.co.za/sites/default/files/publications/pdf/SAJS-113-1-2_de-Beer_ResearchArticle.pdf http://sajs.co.za/sites/default/files/publications/pdf/SAJS-113-1-2_de-Beer_ResearchArticle.pdf