10^5-10^6 colony forming units (cfu)/ml
||Rosenberg E, Koren O, Reshef L, Efrony R, Zilber-Rosenberg I. The role of microorganisms in coral health, disease and evolution. Nat Rev Microbiol. 2007 May5(5):355-62. DOI: 10.1038/nrmicro1635 p.356 right column top paragraphPubMed ID17384666
|| Koren, O. & Rosenberg, E. Bacteria associated with mucus and tissues of the coral Oculina patagonica in summer and winter. Appl. Environ. Microbiol. 72, 5254–5259 (2006). DOI: 10.1128/AEM.00554-06  Ducklow, H. W. & Mitchel, R. Bacterial populations and adaptations in the mucus layers on living corals. Limnol. Oceanogr. 24, 715–725 (1979). link PubMed ID16885273
||Primary source  abstract: "The relative abundance of bacteria in the mucus and crushed tissue of the Mediterranean coral Oculina patagonica was determined by analyses of the 16S rRNA genes of isolated colonies and from a 16S rRNA clone library of extracted DNA. By SYBR gold staining [A technique for counting bacteria and viruses in environmental samples.
Particles that contain either DNA or RNA emit a bright and stable yellow-green fluorescence that can be enumerated by epifluorescence microscopy], the numbers of bacteria in mucus and tissue samples were 6.2 x 10^(7) and 8.3 x 10^(8)/cm^2 of coral surface, respectively, 99.8% of which failed to produce colonies on Marine Agar."
||P.356 left column bottom paragraph: "Initially, research in coral microbiology focused on the mucus layer of the coral structure, using traditional culturing techniques. These studies demonstrated that this layer supports a diverse and abundant beneficial bacterial community [primary source 26, refs 7, 27, 28, 29], including nitrogen fixers [refs 27, 30, 31] and chitin decomposers [primary source 26]. The abundance of bacteria in the mucus layer has been estimated at 10^5–10^6 colony-forming units (cfu) per ml [primary sources 4, 26]."