Proteobacteria

Author: Leandro Alegsa Creation date: November 13, 2022

The Proteobacteria are a major phylum of bacteria.

They are gram-negative bacteria. This means they do not retain the violet dye in the Gram staining protocol.

In a Gram stain test, a counterstain (commonly safranin) is added after the crystal violet, colouring all gram-negative bacteria with a pink colour.

The test itself is useful in classifying two distinct types of bacteria based on the structural differences of their cell walls.

Proteobacteria include a wide variety of pathogens, such as Escherichia coli, Salmonella, Vibrio, Helicobacter, and many other notable genera.

Others are free-living, and include many of the bacteria responsible for nitrogen fixation. The group is defined primarily in terms of ribosomal RNA (rRNA) sequences.

Most members are facultatively or obligately anaerobic, chemoautotrophs, and heterotrophic, but there are numerous exceptions.

There are alphaproteobacteria in this phylum which are widely found in marine plankton. They may constitute over 10% of the open ocean microbial community.

Systematics

The following are some important orders, families, and genera of the eight classes of Proteobacteria. The article Systematics of bacteria is considered a reference in Wikipedia and contains a larger selection of taxa in the phylum Proteobacteria.

Acidithiobacillia

· Order I. Acidithiobacillales

· Acidithiobacillaceae family

· genus Acidithiobacillus

· Thermithiobacillaceae family

· genus Thermithiobacillus

Alphaproteobacteria

· Order I. Rhodospirillales

· Family I. Rhodospirillaceae (non-sulfur-processing purple bacteria)

· Family II Acetobacteraceae; triv. acetic acid bacteria (vinegar)

· Order II Rickettsiales

· Order VI Rhizobiales

· Family I. Rhizobiaceae

· Genus I. Rhizobium

· Family II. Bartonellaceae

· Family III Brucellaceae

and other taxa

Betaproteobacteria

· Order I. Burkholderial

· Order IV Neisseriales

· Family I. Neisseriaceae

· Genus I. Neisseria

· Genus IX Kingella

and other taxa

Gammaproteobacteria

· Order I. Chromatiales

· Family I. Chromatiaceae (triv. sulfur purple bacteria)

· Family II. Ectothiorhodospiraceae

· Order II "Xanthomonadales".

· Family I. "Xanthomonadaceae"

· Genus I. Xanthomonas

· Genus VII Stenotrophomonas

Within the LPSN (List of Prokaryotic names with Standing in Nomenclature), an important listing of the systematics of bacteria, the order Xanthomonadales is no longer listed. This order and the single family Xanthomonadaceae that was added were dissolved due to recent research. Many of the genera are now placed in the order Lysobacterales, others are not yet assigned to any specific order. However, the old system is still in use and is, for example, still used in the taxonomy database of the NCBI (National Center for Biotechnology Information), an important source of information on bacteria.

· Order IV Thiotrichales

· Family I. Thiotrichaceae

· Genus VII Thiomargarita

· Order VIII Pseudomonales

· Family I. Pseudomonaceae

· Genus I. Pseudomonas

· Family II. Moraxellaceae

· Genus I. Moraxella

· Genus II Acinetobacter

· Order X. "Vibrionales"

· Family I. Vibrionaceae

· Genus I. Vibrio

· Order XII. Enterobacterales, previously referred to as order "Enterobacteriales

· Budviciaceae family

· Enterobacteriaceae family

· Erwiniaceae family

· Hafniaceae family

· Morganellaceae family

· Pectobacteriaceae family

· Thorselliaceae family

· Yersiniaceae family

· Order XIII Pasteurellales

· Family I. Pasteurellaceae

· Genus I. Pasteurella

· Genus III. Haemophilus

· Order XIV Oceanospirillales

· Family I. Alcanivoracaceae

· Family II. Hahellaceae

· Family III. Halomonadaceae

· Genus I Halomonas

· Family IV. Litoricolaceae

· Family V. Oceanospirillacae

· Family VI. Oleiphilaceae

· Family VII "Saccharospirillaceae"

and other taxa

Hydrogenophilalia

· Order I. Hydrogenophilic

· Family Hydrogenophilaceae

with only one genus, Hydrogenophilus

Deltaproteobacteria

· Order I. Desulfovibrionales

· Family I. Desulfovibrionaceae

· genus Desulfovibrio

· Order II Myxococcales (Myxobacteria)

· Myxococcaceae family

· Order Bdellovibrionales

· Family Bdellovibrionaceae

· genus Bdellovibrio

and other taxa

Epsilonproteobacteria

· Order Campylobacterales

· Campylobacteraceae family

· genus Campylobacter

· Helicobacteraceae family

· helicobacter genus

· Order Nautiliales

· Family Nautiliaceae

· nautile genus

and other taxa

Oligoflexia

· Order I. Oligoflexal

· Oligoflexaceae family

· Oligoflexus genus

· Order II Silvanigrellales

· Silvanigrellalaceae

· genus Silvanigrella

"Zetaproteobacteria"

· family "Mariprofundaceae", with the only genus Mariprofundus

Questions and Answers

Q: What are Proteobacteria?

A: Proteobacteria are a major phylum of bacteria.

Q: Are Proteobacteria gram-negative or gram-positive bacteria?

A: Proteobacteria are gram-negative bacteria.

Q: What is the Gram staining protocol?

A: The Gram staining protocol is a test used to classify two distinct types of bacteria based on the structural differences of their cell walls.

Q: How does the Gram staining protocol differentiate between gram-negative and gram-positive bacteria?

A: Gram-negative bacteria do not retain the violet dye in the Gram staining protocol, and a counterstain (commonly safranin) is added after the crystal violet, colouring all gram-negative bacteria with a pink colour.

Q: What are some notable examples of pathogens that belong to the Proteobacteria phylum?

A: Some notable examples of pathogens that belong to the Proteobacteria phylum include Escherichia coli, Salmonella, Vibrio, and Helicobacter.

Q: Are all Proteobacteria bacteria pathogens?

A: No, not all Proteobacteria are bacteria pathogens. Others are free-living, and include many of the bacteria responsible for nitrogen fixation.

Q: What are alphaproteobacteria and where can they be found?

A: Alphaproteobacteria are a group of Proteobacteria that are widely found in marine plankton, and may constitute over 10% of the open ocean microbial community.