The genus Fervidobacterium is a group of extremophilic anaerobic Gram-negative rod-shaped bacteria that belongs to the domain Bacteria, phylum Thermotogae, class Thermotogae, order Thermotogales and the family Fervidobacteriaceae. Overall, the phylum Thermotogae contains approximately 47 species distributed in its phylogenetic branches, which have been recently revisited by comparative genomic analysis [1]. The class Thermotogae is divided into orders: Thermotogales, Kosmotogales and Petrotogales. The order Thermotogales includes 2 families: Thermotogaceae and Fervidobacteriaceae. The family Thermotogaceae comprises the genera Thermotoga and Pseudothermotoga, whereas the family Fervidobacteriaceae includes the genera Fervidobacterium and Thermosipho. The order Kosmotogales contains the family Kosmotogaceae, which includes the genera Mesotoga and Kosmotoga, and the order Petrotogales encompasses the family Petrotogaceae, which includes the genera Defluviitoga, Petrotoga, Geotoga, Oceanotoga and Marinitoga [2].

The organisms of the phylum Thermotogae are rod-shaped organisms with a “toga”, shaped envelope, which gives the phylum its name. They are Gram-negative, strictly anaerobic, fermentative and thermophilic, withstanding temperatures that can vary between 40 °C and 100 °C. The organisms belonging to this phylum are commonly found in geothermal basins, oil wells, pipelines, refineries and biodigesters, as these places share favourable characteristics such as the absence of oxygen, abundant organic matter and high temperatures [[3], [4], [5]]. The genera belonging to the phylum Thermotogae have an extensive history of reports on proteins and enzymes produced by them. Their metabolic and biochemical machinery is associated with the degradation of petroleum derivatives, keratin, as well as the most diverse substrates [[6], [7], [8]].

Regarding the genus Fervidobacterium, it comprises the species F. changbaicum, F. gondwanense, F. islandicum, F. nodosum, F. pennivorans, F. riparium and F. thailandense. All of them have common morphological and physiological characteristics, which are cells in the form of short rods, the presence of a spheroid toga at their end, they are tolerant to high temperatures, and they use various carbon sources, which allows them to explore different substrates. These species are widely reported in terms of enzyme production, with remarkable thermostability. It arouses biotechnological interest on the genus regarding the bioprospection of high added value enzymes [6,9,10].

The ecological diversity of the genus Fervidobacterium has already been identified in samples of water, soil, animals and even plants; however, its greatest abundance is reported in aquatic samples [11]. For example, our research group, in a recent metagenomic analysis, identified the genus Fervidobacterium, with relative abundance above 60 %, in sludge samples from a Multifactory Wastewater Treatment Plant (MF-WWTP), located in an industrial complex in the municipality of Jaboatão dos Guararapes, state of Pernambuco, Brazil (8°06′23.1″S and 35°01′36.0″W) (manuscript in preparation).

In addition to the genus Fervidobacterium, our metagenomic analysis also identified the genera Kosmotoga, Petrotoga, Thermosipho and Thermotoga. Since Fervidobacterium is the genus with the greatest abundance in our analyses, we understand the importance of conducting a literature search on it. Hence, this literature search aimed to perform a literature review on the genus Fervidobacterium. This study will objectively address the global distribution of the 16S rRNA gene sequences found for the genus, as well as the environment where it was isolated, its morphological characteristics, and the thermoenzymes produced by the species belonging to this genus, indicating its biotechnological potential and applications.