Sunday 4 August 2013

Microbiology of the skin: glossary of terms

Here is a useful glossary of terms relating to the microbiology of human skin:

  • Keratinocyte
    The predominant cell type of the epidermis. 
    Keratinocytes produce keratin as they terminally differentiate into the squames of the stratum corneum
  • Squame
    An enucleated, dead, squamous keratinocyte that is shed from the stratum corneum
  • Sebum
    The oily, lipid-containing substance that is secreted by the sebaceous glands of the skin.
    Sebaceous glands are connected to the hair follicle and form the pilosebaceous unit. Sebum protects and emolliates the skin and hair
  • 16S ribosomal RNA metagenomic sequencing
    Genomic analysis of 16S ribosomal RNA phylotypes from DNA that is extracted directly from bacterial communities in clinical or environmental samples, a process that circumvents culturing
  • Microbiome
    All of the genetic material of a microbial community sequenced together
  • Phylotype
    A taxon-neutral way to describe organisms based on their phylogenetic relationships to other organisms. 
    Phylotypes are determined by comparing 16S ribosomal RNA gene sequences. A common threshold used to define species-level phylotypes is 97% sequence identity of the 16S rRNA gene sequence
    Whole-genome shotgun metagenomic sequencing
    Genomic analysis of DNA that is extracted directly from a clinical or environmental sample and whole-genome shotgun (WGS) sequenced to represent the full microbiome
  • Pattern recognition receptor (PRR)
    A receptor present on the surface of keratinocytes and other cells of the innate immune system that recognizes microorganism-specific molecules (for example, lipopolysaccharide and flagellin)

  • Pathogen-associated molecular pattern (PAMP)
    A molecule that is associated with a pathogen and recognized by a pathogen recognition receptor. Examples include lipopolysaccharide, flagellin, lipoteichoic acid, double-stranded RNA, peptidoglycan and unmethylated CpG motifs
  • Atopic dermatitis (AD)
    A type of eczema characterized by red, flaky, itchy skin, typically affecting the inner elbows and behind the knees. It is often associated with other atopic diseases such as allergic rhinitis, hay fever and asthma
  • Seborrhoeic dermatitis
    An inflammatory, hyperproliferative skin condition characterized by red, flaky, skin often affecting sebaceous areas of the face, scalp and trunk. Commonly known as dandruff

Posted by Tim Sandle

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