title: AntifungalStreptomycesspp. Associated with the Infructescences ofProteaspp. in South Africa.
abstract: Common saprophytic fungi are seldom present inProteainfructescences, which is strange given the abundance of mainly dead plant tissue in this moist protected environment. We hypothesized that the absence of common saprophytic fungi inProteainfructescences could be due to a special symbiosis where the presence of microbes producing antifungal compounds protect the infructescence. Using a culture based survey, employing selective media andin vitroantifungal assays, we isolated antibiotic producing actinomycetes from infructescences ofProtea repensandP.neriifoliafrom two geographically separated areas. Isolates were grouped into three different morphological groups and appeared to be common in theProteaspp. examined in this study. The three groups were supported in 16S rRNA and multi-locus gene trees and were identified as potentially novelStreptomycesspp. All of the groups had antifungal activityin vitro.Streptomycessp. Group 1 had inhibitory activity against all tested fungi and the active compound produced by this species was identified as fungichromin.Streptomycesspp. Groups 2 and 3 had lower inhibition against all tested fungi, while Group 3 showed limited inhibition againstCandida albicansandSporothrixisolates. The active compound for Group 2 was also identified as fungichromin even though its production level was much lower than Group 1. The antifungal activity of Group 3 was linked to actiphenol. The observed antifungal activity of the isolated actinomycetes could contribute to protection of the plant material against common saprophytic fungi, as fungichromin was also detected in extracts of the infructescence. The results of this study suggest that the antifungalStreptomycesspp. could play an important role in defining the microbial population associated withProteainfructescences.
authors.affiliation: Department of Microbiology and Plant Pathology, Forestry and Agriculture Biotechnology Institute, University of Pretoria Pretoria, South Africa.
authors.forename: Zander R
authors.initials: ZR
authors.lastname: Human
authors.affiliation: Natural Products Research Institute, College of Pharmacy, Seoul National University Seoul, Republic of Korea.
authors.forename: Kyuho
authors.initials: K
authors.lastname: Moon
authors.affiliation: Natural Products Research Institute, College of Pharmacy, Seoul National University Seoul, Republic of Korea.
authors.forename: Munhyung
authors.initials: M
authors.lastname: Bae
authors.affiliation: Department of Microbiology and Plant Pathology, Forestry and Agriculture Biotechnology Institute, University of Pretoria Pretoria, South Africa.
authors.forename: Z Wilhelm
authors.initials: ZW
authors.lastname: de Beer
authors.affiliation: Department of Chemistry, Hankuk University of Foreign Studies Yongin, Republic of Korea.
authors.forename: Sangwon
authors.initials: S
authors.lastname: Cha
authors.affiliation: Department of Microbiology and Plant Pathology, Forestry and Agriculture Biotechnology Institute, University of Pretoria Pretoria, South Africa.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Wingfield
authors.affiliation: Department of Genetics, Forestry and Agriculture Biotechnology Institute, University of Pretoria Pretoria, South Africa.
authors.forename: Bernard
authors.initials: B
authors.lastname: Slippers
authors.affiliation: Natural Products Research Institute, College of Pharmacy, Seoul National University Seoul, Republic of Korea.
authors.forename: Dong-Chan
authors.initials: DC
authors.lastname: Oh
authors.affiliation: Department of Microbiology and Plant Pathology, Forestry and Agriculture Biotechnology Institute, University of Pretoria Pretoria, South Africa.
authors.forename: Stephanus N
authors.initials: SN
authors.lastname: Venter
keywords: Candida albicans; Protea; Sporothrix; Streptomyces; actiphenol; antifungal; fungichromin; infructescence