SAPROSPIRAE

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KINGDOM SAPROSPIRAE

INTRODUCTION TO THE KINGDOM SAPROSPIRAE AND ITS SINGLE PHYLUM, SAPROSPIROBACTERIA

Saprospirae (sap-ro-SPI-re) is formed from a Greek root which means rotten (sapros -σαπρός) and a Latin root that means spiraled (spira). The describes the nature of Saprospira, the genus after which the kingdom was named.

These are gram negative rods that occur singly or in filaments. Usually they occur within a layer of slime through which they can glide. Cytophaga (Figure A) and its relatives are important cellulose decomposers in soil and water. Beggiatoa (Figure B) is chemoautotrophic and reduces carbon dioxide by oxidizing hydrogen sulfide to elemental sulfur.

A. Cytophaga, a common soil microbe that efficiently breaks down cellulose.

B. Beggiatoa, a filamentous bacterium that oxidizes hydrogen sulfide.

Images taken from:
A: http://genome.jgi-psf.org/finished_microbes/cythu/cythu.home.html
B: http://user.uni-frankfurt.de/~schauder/gradient/beggia06_bg.jpg

SYNOPTIC DESCRIPTION OF THE SAPROSPIROBACTERIA

The following description comes mainly from Margulis and Schwartz (1998), Barnes (1984), Brock et al. (1994), and Tudge (2000).

I. SYNONYMS: Gliding bacteria.

II. PHYLUM CHARACTERISTICS:

A. Structure

Cell Form: Variable; rods that occur singly or in chains (filaments).

Cell Wall: Gram-.

Motility: Non-motile but cells can glide on surfaces; they are often embedded in polysaccharide slime.

B. Physiology

O₂ Tolerance: Aerobes; some facultative anaerobes.

Substrates: Quite variable, some are parasites of animals; some feed on carbohydrates, cellulose, and chitin, while others may be chemoautotrophic by the oxidation of H₂S.

Products: Typical aerobes with a well-developed citric acid cycle and cytochrome system; thus, they release CO₂ as a consequence of respiration. Some, like Beggiatoa, are autotrophic or mixotrophic and fix CO₂ with the oxidation of inorganic sulfur. In particular, they often deposit sulfur granules in the cells.

C. Other: Very diverse group of bacteria.

D. Ecology: Free-living in soils and aquatic sediments, some commensals and parasites.

SYSTEMATICS OF THE SAPROSPIROBACTERIA

This is a modification of Margulis and Schwartz (1998) who separate the gliding bacteria (Saprospirobacteria B-6) from the fruiting bacteria (Myxobacteria) based on 16S rRNA studies. Bergey's Manual of Systematic Bacteriology, volume 3, section 23 (Holt 1989a; Nonphotosynthetic, Nonfruiting Gliding Bacteria) includes the taxa which I place in the Class Cytophagatia. Bergey's Manual of Systematic Bacteriology, 2nd edition (Garrity et al. 2001) treats the taxa that I include in the Saprospirae as a group within the Gammaproteobacteria together with a separate phylum (Phylum B XX. "Bacteroidetes"). I present the kingdom with a single phylum that has a single class. Almost certainly this is a paraphyletic group, and the taxa will be revised as information becomes available.

HIERARCHICAL CLASSIFICATION OF THE SAPROSPIROBACTERIA

This system follows Margulis and Schwartz (1998) who treat the gliding bacteria as a taxon that is distinct from the Myxobacteria, with which they are usually associated. As I give them here, the gliding bacteria occupy a kingdom with a single phylum and a single class that has two orders.

CLASS CYTOPHAGATIAE

ORDER CYTOPHAGIALES

Slender, single rods, sometimes in chains, but without fruiting bodies; they may or may not make cysts, some are facultative anaerobes and ferment carbohydrates to organic acids; usually aerobic decomposers of chitin and cellulose; in soil and aquatic systems, some parasites of fish.

Cytophaga, Sporocytophaga, Saprospira, Microscilla, Flexibacter.

ORDER BEGGIATOIALES

Straight or helical filaments, sessile and attached or mobile filaments; may multiply by random fragmentation of the filaments; some oxidize H₂S with the deposition of internal S granules (chemoautotrophic or chemoheterotrophic); in aquatic systems and oral cavities of animals.

Beggiatoa, Thiofilum, Leucothrix, Simonsiella, Alysiella, Vitreoscilla.

This page is maintained by Jack R. Holt. Last revised: 04/22/2008.