{{short description|Family of bacteria}} {{Automatic taxobox | taxon = Xanthobacteraceae | authority = Lee ''et al''. 2005 | subdivision_ranks = Genera | subdivision_ref = <ref name="LPSN">{{cite web |vauthors=Euzéby JP, Parte AC |title=''Xanthobacteraceae'' |url=https://lpsn.dsmz.de/family/xanthobacteraceae |access-date=May 15, 2021 |work=List of Prokaryotic names with Standing in Nomenclature (LPSN)}}</ref> | subdivision = * ''Ancylobacter'' <small>Raj 1983</small> * ''Angulomicrobium'' <small>Vasil'eva ''et al''. 1986</small> * ''Aquabacter'' <small>Irgens ''et al''. 1993</small> * ''Azorhizobium'' <small>Dreyfus ''et al''. 1988</small> * ''Labrys'' <small>Vasilyeva and Semenov 1985</small> * ''Methylorhabdus'' <small>Doronina ''et al''. 1996</small> <!-- Microcyclus was reclassified as Ancylobacter. --> <!-- Pseudolabrys was transferred to the family Nitrobacteraceae. --> <!-- Pseudoxanthobacter was transferred to the family Pseudoxanthobacteraceae. --> * ''Starkeya'' <small>Kelly ''et al''. 2000</small> * ''Xanthobacter'' <small>Wiegel ''et al''. 1978 (Approved Lists 1980)</small> | synonyms = * "Labriaceae" <small>Beck ''et al''. 2015</small><ref name="Beck">{{Cite journal | doi = 10.1111/1462-2920.12736 | title = Multiphyletic origins of methylotrophy in ''Alphaproteobacteria'', exemplified by comparative genomics of Lake Washington isolates | journal = Environmental Microbiology | volume = 17 | issue = 3 | pages = 547–54 | year = 2015 | last1 = Beck | first1 = D. A. C. | last2 = McTaggart | first2 = T. L. | last3 = Setboonsarng | first3 = U. | last4 = Vorobev | first4 = A. | last5 = Goodwin | first5 = L. | last6 = Shapiro | first6 = N. | last7 = Woyke | first7 = T. | last8 = Kalyuzhnaya | first8 = M. G. | last9 = Lidstrom | first9 = M. E. | last10 = Chistoserdova | first10 = L. | pmid=25683159| bibcode = 2015EnvMi..17..547B | doi-access = free }}</ref> }}

The '''Xanthobacteraceae''' are a family of bacteria that includes ''Azorhizobium'', a genus of rhizobia. Xanthobacteraceae bacteria are diverse and Gram-negative, rod-shaped, and may be motile or non-motile depending on the specific bacteria. Their cells range in size from 0.4–1.0 × 0.8–6 μm,<ref name="Wiegel_2015">{{cite book |title=Bergey's Manual of Systematics of Archaea and Bacteria |vauthors=Wiegel JK |date=2015 |publisher=American Cancer Society |isbn=978-1-118-96060-8 |pages=1–22 |chapter=Xanthobacter |doi=10.1002/9781118960608.gbm00829}}</ref> but when grown in the presence of alcohol as the sole carbon source, they can reach up to 10 μm in length. These bacteria do not form spores and have opaque, slimy colonies that appear slightly yellow due to the presence of zeaxanthin dirhamnoside.<ref name="Oren_2014">{{cite book |title=The Prokaryotes: Alphaproteobacteria and Betaproteobacteria |vauthors=Oren A |date=2014 |publisher=Springer |isbn=978-3-642-30197-1 |veditors=Rosenberg E, DeLong EF, Lory S, Stackebrandt E |place=Berlin, Heidelberg |pages=709–726 |chapter=The Family Xanthobacteraceae |doi=10.1007/978-3-642-30197-1_258}}</ref>

The genus ''Xanthobacter'' was established in 1978 by Wiegel et al. based on numerical taxonomic comparisons of microorganisms that were then classified in the genus ''Corynebacterium''. In 2005, Lee et al. proposed the family Xanthobacteraceae based on a comparison of 16S rRNA of the members of ''Alphaproteobacteria''. The family includes five genera, namely ''Xanthobacter'', ''Azorhizobium'', ''Ancylobacter'', ''Labrys'', and ''Starkeya''.<ref name="Oren_2014" />

== Phenotypic properties == The ''Xanthobacteraceae'' family is highly diverse, with some cells being polymorphic in shape. Their cells have a Gram-negative type cell wall and contain ubiquinone Q-10 as their major respiratory quinone. Refractile (phosphate) and lipid bodies are evenly distributed throughout the cells. However, as cells also contain polyphosphate granules, sometimes the Gram reaction can give false positive results.

Most chemolithoautotrophic strains of ''Xanthobacteraceae'' require H<sub>2,</sub> O<sub>2</sub> and CO<sub>2</sub> in mineral media,<ref name="Oren_2014" /> while chemoorganoheterotrophic strains utilize various carbon sources such as methanol, ethanol, n-propanol, n-butanol, and different organic acids. Some genera within the family demonstrate the ability to fix nitrogen under reduced oxygen pressure.<ref name="Oren_2014" />

== Genotype of ''Xanthobacteraceae'' == On average the chromosomes are 4.77–5.37 Mbp in length. In ''Azorhizobium caulinodans'', ''Starkeya novella'', and ''X. autotrophicus,'' there are 4417–4847 predicted genes presents in the genome. A 316-kb plasmid containing 308 genes present in ''X. autotrophicus'' Py2 strains.<ref>{{cite journal | vauthors = Lee KB, De Backer P, Aono T, Liu CT, Suzuki S, Suzuki T, Kaneko T, Yamada M, Tabata S, Kupfer DM, Najar FZ, Wiley GB, Roe B, Binnewies TT, Ussery DW, D'Haeze W, Herder JD, Gevers D, Vereecke D, Holsters M, Oyaizu H | display-authors = 6 | title = The genome of the versatile nitrogen fixer Azorhizobium caulinodans ORS571 | journal = BMC Genomics | volume = 9 | issue = 1 | pages = 271 | date = June 2008 | pmid = 18522759 | pmc = 2443382 | doi = 10.1186/1471-2164-9-271 | doi-access = free }}</ref>

== Ecology == Members of the genus can be found in freshwater, wet soil that contains decaying organic materials and in the sediments.<ref name="Wiegel_2015" />{{rp|1–25}} Rice paddies, soils environments, freshwater habitats such as ponds, creeks and lakes contain ''Ancylobacter aquaticus.'' Study showed that there is a relationship between the watershed urbanization and the alteration of bacterial community composition. ''Xanthobacteraceae'' consistently showed decreased abundance on increasing watershed urbanization.<ref name=":22">{{cite journal | vauthors = Simonin M, Voss KA, Hassett BA, Rocca JD, Wang SY, Bier RL, Violin CR, Wright JP, Bernhardt ES | display-authors = 6 | title = In search of microbial indicator taxa: shifts in stream bacterial communities along an urbanization gradient | journal = Environmental Microbiology | volume = 21 | issue = 10 | pages = 3653–3668 | date = October 2019 | pmid = 31125479 | doi = 10.1111/1462-2920.14694 | bibcode = 2019EnvMi..21.3653S | doi-access = free }}</ref>

== Phages == There are three known phages that can infect ''Xanthobacter autotrophicus'' strain GZ29.<ref>{{Cite journal| vauthors = Wilke D, Schlegel HG |title=A defective generalized transducing bacteriophage in Xanthobacter autotrophicus GZ29 |journal=J Gen Microbiol |date=1979 |volume=115 |issue=2 |pages=403–410|doi=10.1099/00221287-115-2-403 |doi-access=free }}</ref> There are two lytic phages named CA1 and CA2. Both have head of 61-68&nbsp;nm in diameter. CA1 has a 98-100&nbsp;nm tails while the length of tail for CA2 is 166-175&nbsp;nm. The third phage called CA3 is lysogenic in nature and contain head of 37-43&nbsp;nm and a tail of 43-50&nbsp;nm in length. CA3 also contains a small DNA molecule of 3.3 kDa.<ref name="Oren_2014" />

== ''In vitro'' growth condition and maintenance == Most of the strains can grow chemolithoautotrophically in the mineral media in the presence of H<sub>2,</sub> O<sub>2</sub> and CO<sub>2</sub>. Other strains can grow chemoorganoheterotrophically on methanol, ethanol, propanol, n-butanol and organic acids. Temperature for optimal growth varies from 25–42&nbsp;°C.<ref name="Oren_2014" /> Generally, they can grow at pH 6.5-8 with optimum growth at pH 7.5. Some strains decrease the pH of the medium during growth. Therefore, addition of buffer is recommended to maintain the optimal growth.<ref name="Wiegel_2015" /> Cultures can be maintained for 10 months at 2-5&nbsp;°C in liquid medium and for up to 15 months in sealed agar slants. At -20&nbsp;°C, the culture can be stored for 3 years in the presence of 60% (v/v) glycerol. Lyophilization is recommended for long term storage.<ref name="Oren_2014" /><ref name="Wiegel_2015" />

== Pathogenicity and antibiotic sensitivity == There is no known pathogenic strain found in the ''Xanthobacteraceae.'' Some species of genus Azorhizobium are associated with plant such as Sesbania and some other leguminous plants that live in symbiosis.<ref name="Oren_2014" /> Some species of ''Xanthobacteraceae'' are sensitive to penicillin, novobiocin and polymyxin B. ''X. autotrophicus and X. flavus'' are resistant to erythromycin and bacitracin.<ref name="Wiegel_2015" />

== Application == ''Xanthobacteraceae'' species, including X. ''viscosus'' and X. ''aminoxidans'', are commonly found in activated sludge from water treatment plants, indicating their potential role in organic compound degradation within polluted environments.<ref name="Oren_2014" /> Recent studies have uncovered the biotechnological applications of ''Xanthobacter'' species. Some bacteria within this family can degrade toxic compounds, such as polycyclic aromatic compounds (PAHs), into CO<sub>2</sub> and water. Furthermore, certain ''Xanthobacteraceae'' strains, such as ''Starkeya'' sp. strain N1B, can use toxic aromatic hydrocarbons like naphthalene as their sole carbon source for bacterial cellulose production.<ref name=":22" /> This process results in the production of cellulosic biofilm using toxic compounds, such as naphthalene Christal.

==Phylogeny== The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN).<ref name="LPSN"/> The phylogeny is based on whole-genome analysis.<ref name="Hördt">{{cite journal |vauthors=Hördt A, García López M, Meier-Kolthoff JP, Schleuning M, Weinhold L, Tindall BJ, Gronow A, Kyrpides NC, Woyke T, Göker M |year=2020 |title=Analysis of 1,000+ Type-Strain Genomes Substantially Improves Taxonomic Classification of ''Alphaproteobacteria'' |journal=Front. Microbiol. |volume=11 |pages=468 |doi=10.3389/fmicb.2020.00468 |pmid=32373076 |pmc=7179689| doi-access=free}}</ref>

{{Clade | style=font-size:100%;line-height:50% |1={{clade |label1='''''Xanthobacteraceae''''' |1={{clade |1={{clade |1={{clade |1={{clade |1=''Starkeya'' |2={{clade |1=''Methylorhabdus'' |2=''Angulomicrobium'' }} }} |2=''Ancylobacter'' }} |2={{clade |1=''Aquabacter'' |2={{clade |1=''Xanthobacter'' |2=''Azorhizobium'' }} }} }} |2=''Labrys'' }} |label2=outgroup |2=''Blastochloridaceae'' }} }}

== References == {{Reflist}}

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Category:Hyphomicrobiales Category:Bacteria families