Fervidobacterium islandicum

Fervidobacterium islandicum cells are Gram-negative motile rods, about 1.8 μm in length, and 0.6 μm in width occurring singly or in pairs.^[1] About 50% of cells form large spheroids at one end known as a 'toga' commonly found in members of the phylum Thermotogota (formerly Thermotogae)^[2]

Fervidobacterium islandicum isolate H21 grows in a pH range from 6.0 to 8.0 with an optimum at around 7.2.^[1] Growth is observed at a temperature range between 40 °C and 80 °C, with an optimum of 70 °C.^[3] At a temperature of 65 °C, strain H21 has a doubling time of 150 minutes.^[1]

Growth of isolate H21 requires low amounts (0.3%) of yeast extract. When this is used as a single carbon and energy source, the final cell concentration is 1×10⁷ cells/ml.^[1] Growth is strongly enhanced by the addition of 0.2% pyruvate, ribose, glucose, maltose, raffinose, starch and, less efficiently, cellulose. Final cell concentrations with these additions can range from 2 to 5×10⁸.^[1] In the presence of glucose, F. islandicum produces the following end products: L(+) lactate, acetate, ethanol, H₂ and CO₂.^[1] Isolate H21 shows a sensitivity to common antibiotics, its growth is inhibited by addition of vancomycin, streptomycin, ampicillin, chloramphenicol and rifampicin at 10 ${\displaystyle \mu }$g/ml.^[1]

Fervidobacterium islandicum strain AW-1 has a total genome size of 2.4 million base pairs, which is slightly larger than the genomes of other Fervidobacterium strains.^[3] It has a G + C content of 40.7%.^[3] It contains 2,184 protein coding genes in a total of 2,248 genes.^[3]

Fervidobacterium islandicum was originally isolated from an Icelandic hot spring on the banks of the river Varma close to Hverager${\displaystyle \eth }$i, Iceland. The anaerobic samples were taken from hot waters and muds.^[1] Here, the temperatures were between 70 °C and 102 °C, and the pH was between 1.5 and 9.^[1]

Fervidobacterium islandicum AW-1 is capable of complete feather degradation at 70 °C and a pH of 7.^[4] Feather keratin has a very high cysteine content, which makes it very rigid and hard to digest.^[5] 5 million tons of chicken feathers are generated by the poultry industry every year, making chicken feathers a serious solid waste problem.^[4] Therefore, F. islandicum's ability to degrade native chicken feathers is very appealing.^{[citation needed]}