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Firmicutes
Scientific classification
Kingdom: Bacteria Division: Firmicutes
Classes
Bacilli Clostridia Mollicutes

The Firmicutes, or Endobacteria, are a division of bacteria, most of which have Gram-positive cell wall structure. A few, the Mollicutes or mycoplasmas, lack cell walls altogether and so do not respond to Gram staining, but still lack the second membrane found in other Gram-negative forms. Others, such as Megasphaera, Pectinatus, Selenomonas, and Zymophilus have a porous pseudo-outer-membrane that causes them to stain Gram-negative. Originally the Firmicutes were taken to include all Gram-positive bacteria, but more recently they tend to be restricted to a core group of related forms, called the low G+C group in contrast to the Actinobacteria. They have round cells, called cocci (singular coccus), or rod-shaped forms.

Many Firmicutes produce endospores, which are resistant to desiccation and can survive extreme conditions. They are found in various environments, and some notable pathogens. Those in one family, the heliobacteria, produce energy through photosynthesis.

Contents 1 Classes 2 Genera 3 Additional information 4 References

The group is typically divided into the Clostridia, which are anaerobic, the Bacilli, which are obligate or facultative aerobes, and the Mollicutes. On phylogenetic trees the first two groups show up as paraphyletic or polyphyletic, as do their main genera, Clostridium and Bacillus. It is likely these groups will undergo revision.

While there are currently more than 274 genera within the Firmicutes phylum, Notable genera of Firmicutes include:

Bacilli, order Bacillales

• Bacillus
• Listeria
• Staphylococcus

Bacilli, order Lactobacillales

• Enterococcus
• Lactobacillus
• Lactococcus
• Leuconostoc
• Pectinatus
• Pediococcus
• Streptococcus

Clostridia

• Acetobacterium
• Clostridium
• Eubacterium
• Heliobacterium
• Heliospirillum
• Sporomusa

Mollicutes

• Mycoplasma
• Spiroplasma
• Ureaplasma
• Erysipelothrix'

Firmicutes play an important role in beer, wine, and cider spoilage.

Researcher Jeffrey Gordon and his colleagues found that obese humans and mice had a lower percentage of a family of bacteria called Bacteroidetes and more Firmicutes. But they are not sure if Firmicutes cause obesity or if people who are obese grow more of that type of bacteria.

• Seth Borenstein "Scientists link weight to gut bacteria" , Yahoo News, December 20, 2006 (Link dead as of 22:07, 14 January 2007 (UTC))
• ROBIN MARANTZ HENIG "Fat Factors" , New York Times Magazine, August 13, 2006
• ( Ley et al. 2006) "Obesity alters gut microbial ecology" , Proceedings of the National Academy of Sciences of the United States of America, August 2, 2005