A Microbial Biorealm page on the genus Ignavibacterium album
Higher order taxa
Domain: Bacteria; Phylum: Chlorobi; Class: Ignavibacteria; Order: Ignavibacteriales; family: Ignavibacteriaceae
Description and significance
A thermophilic chemoheterotrophic microorganism that was isolated from microbial mats discovered in aqueous hot-springs of Yumata, Japan. Once isolated, it was found that I. album was a gram-negative rod that is non-sporulating, non-motile and strictly anaerobic microbe with rods ranging from 2.0 to 15.5 μm and a generation time of 78.8 hours in an isolated system in a laboratory setting. Although this microorganism has been successfully isolated and cultured, it has yet to be proven useful in any developed culture, technology or medical diagnostics. Though not a disease-causing agent, I. album has been found to be susceptible to antibiotics such as tetracycline and vancomycin, while resistant towards ampicillin and streptomycin. The significance of these findings has not yet been determined.
The chromosome of Ignavibacterium album is both singular and circular. Via the analysis of its genome, multiple interesting features have been found. The genome of I. album contains a variety of protein coding sequences with a number of frame-shift mutations encoding for nonfunctional proteins, while also lacking both chlorosomes and photosynthetic-coding proteins, unlike its neighboring microorganism, Green Sulfur Bacteria who belongs to the same same phylum, Chlorobi, but shares a genomic sequence of only 77-83% of each other. This value of similarity falls just short of the cut-off value of 85% to present I. album in its own phylum. Lastly, there was evidence to suggest that the genome of this microorganism contains genes that encode for a variety of electron transfer complexes suggesting that I. album may have the ability to perform organoheterotrophy.
Cell and colony structure
Ignavibacterium album displays he ability to achieve growth between the temperatures of 30° C to 55° C and when exposed to a pH between 6.5 and 8; with its optimum criteria for growth being 45° C and a pH of 7. No growth is observed outside of the ranges of temperature and pH indicated above. The colonies of I. album are capable of growing large enough to become visible to the naked eye within their generation time of 78.8 hours. I. album grows in the for of short rods of 2.0 μm to larger rods of 15.5 μm, while appearing colorless. Two common cellular structures, flagella and chlorosomes, were not appreciated; this indicate that the microorganism is both non-motile and incapable of preforming photosynthesis.
Ignavibacterium album appears to have a versatile metabolism by being a moderate thermophilic chemoheterotroph, thus allowing the microbe to gain its energy through the means of the oxidation of electron donors for ATP synthesis and preventing the microbe from using carbon dioxide as its carbon source in the production of its very own organic compounds. Therefore, I. album resorts to the use of sulfur, carbohydrates, lipids and proteins as its carbon sources. As previously mentioned, I. album possesses a specific gene cluster that encodes for a variety of electron transfer complexes including the RNF complex. This complex creates a sodium gradient across the cytoplasmic membrane that plays a key role in the production of ATP when ferredoxins are oxidized by NAD+. This mechanism is also capable of working in the opposite direction, where NADH is oxidized and ferredoxins are reduced. A ferredoxin is a group of iron and sulfur containing proteins that function as electron carriers for some anaerobic bacteria such as I. album. When the catalase and oxidase tests have been performed in a laboratory setting, the microbe has been found to be negative because the genome of I. album does not possess a protein that codes for catalase. Due to its strict anaerobic criteria, this microbe grows fermentatively, producing two net ATP molecules, along with two molecules of lactate or two alcohol molecules accompanied with 2 carbon dioxide molecules.
Although there seems to be no relationship that has been determined with regards to this microorganism being a disease-causing agent in humans, plants, or animals, there has been some experimentation involving the application of antibiotic treatments. I. album was found to be susceptible to a variety of strong antibiotics such as vancomycin and tetracycline, while it was found to be resistant to ampicillin and streptomycin.
http://link.springer.com/referenceworkentry/10.1007/978-3-642-38954-2_143; Eugene Rosenberg, Edward F. DeLong, Stephen Lory, Erko Stackebrandt, and Fabiano Thompson. The family ignavibacteriacaea. The prokaryotes: other major lineages of bacteria and the archaea. October 2014 19:701-703. [doi: 10.1007/978-3-642-38954_143.]
http://ijs.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.012484-0; Takao Iino, Koji Mori, Yoshihito Uchino, Tatsunori Nakagawa, Shigeaki Harayama, and Ken-ichiro Suzuki. Ignavibacterium album gen. nov., sp. nov., a moderately thermophilic anaerobic bacterium isolated from microbial mats at a terrestrial hot spring and proposal of Ignavibacteria classis nov., for a novel lineage at the periphery of green sulfur bacteria. Int J Syst Evol Microbiol June 2010 60: 1376-1382. [doi: 10.1099/ijs.0.012484-0.]
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3362086/; Zhenfeng Liu, Niels-Ulrik Frigaard, Kajetan Vogl, Takao Iino, Moriya Ohkuma, Jörg Overmann, and Donald A. Bryant. Complete genome of Ignavibacterium album, a metabolically versatile, flagellated, facultative anaerobe from the phylum chlorobi. Front Microbiol 2013 3: 185. [10.3389/fmicb.2012.00185.]
Edited by Chelbie Aube of Dr. Lisa R. Moore, University of Southern Maine, Department of Biological Sciences, http://www.usm.maine.edu/bio