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Editorial |

Skin Microecology The Old and the New

Guy F. Webster, MD, PhD
Arch Dermatol. 2007;143(1):105-106. doi:10.1001/archderm.143.1.105.
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Interest in the ecology of skin bacteria and the skin as a habitat has waxed and waned over the past 30 or so years. The past few years have been a particularly active time as were the 1970s. Thirty years ago, a wealth of research demonstrated that different regions of the skin have distinct and reproducible bacterial populations that are determined by the cutaneous anatomy.1

Three major factors were shown to determine the skin habitats: moisture, lipids, and the ability to maintain a reduced environment. Sebum is the most potent determinant of skin flora. Prior to the pubertal surge in testosterone, sebaceous glands are inactive and the skin microflora is greatly reduced. After puberty, in areas where sebum is plentiful, such as the head and upper trunk, there is a stable population of lipophilic organisms numbering in the tens of millions. The anaerobic propionibacteria dominate the region by virtue of an extracellular lipase that liberates glycerol from sebaceous triglycerides, which is then used as a carbon source. The fatty acids are unused by the bacteria and remain in sebum. The sebaceous gland provides a second ecological determinant, an enclosed relatively anoxic crypt where facultative anaerobes like propionibacteria can survive in the depths and lipophilic aerobes such as yeast of the Malassezia genus occupy the acroinfundibulum.13

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