# The Marine Bacterial Genus _Euzebya_ Is Distributed Worldwide in Terrestrial Environments: A Review
## 1 Introduction  
In terms of microbial diversity, the oceans represent the largest biosphere habitat, containing about 70% of the prokaryotic biomass [1]. In recent decades, interest in the bioactive compounds from marine bacteria has grown enormously [2; 3; 4; 5; 6; 7; 8], and many works have focused on rare marine _Actinomycetota_[9; 10; 11; 12; 13]. One of the most intriguing and rare genera of marine _Actinomycetota_ is _Euzebya_. No terrestrial _Euzebya_ has been isolated so far.  
The genus _Euzebyua_ was described by [PERSON] et al. [14] to accommodate a Gram-positive actinobacterial strain isolated from the epidermis of _Holothuria edulis_, a sea cucumber collected in the Sea of Japan. The strain was characterized by a reddish-orange or tangerine color and was able to grow in sodium chloride concentrations of 0.5-12%, but no growth was observed in the absence of sodium chloride or at a concentration of 15%. Optimal growth temperatures were in the range of 20-28 \({}^{\circ}\)C and pH 7-9. No growth was obtained at pH 6 or 10. The type strain is _Euzebyua tangerina_ from the new order _Euzebyales_ and the new family _Euzebyaceae_[14]. A second member of the genus, _Euzebya rosea_, was isolated from the waters of the East China Sea and showed a light pink color, optimal growth at 25-30 \({}^{\circ}\)C, and pH 6-7. Optimal sodium chloride concentrations were 1-4% [15].  
_Euzebya peticza_ was the third species of the genus, isolated from seawater collected at 150 m depth in the Eastern Pacific Ocean [16]. Colonies were pink, with optimal growth at30-35 \({}^{\circ}\)C, in sodium chloride concentrations of 1-2%, and pH 6.5. This last species could grow in the absence of sodium chloride. The complete genome sequence of _E. pacitica_ revealed its ecological roles in marine carbon, nitrogen, phosphorus, and sulfur cycles [17]. In general, the three marine species of _Euzebya_ are characterized by their tolerance to relatively high sodium chloride concentrations, growth at neutral pH (7), and temperatures from 20 to 35 \({}^{\circ}\)C.  
The advent of molecular tools, particularly next-generation sequencing (NGS), has dramatically changed the knowledge of the diversity of microbial life on Earth. In recent decades, many studies on different terrestrial environments, including caves [18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36], have described the diversity and abundance of _Euzebyales/Euzebyaceae/Euzebya_; however, as far as we know, no _Euzebya_ isolates have been obtained from terrestrial niches. This prompted us to review the habitats where _Euzebya_ sequences were found and their ecological requirements in order to understand the failures in the adoption of isolation protocols that led to the lack of terrestrial isolates. The diversity and abundance of _Euzebyales/Euzebyaceae/Euzebya_ in most terrestrial environments are intriguing and its role in the geochemical cycle of elements is unknown, and thus the isolation of _Euzebya_ strains could help to understand why this abundant bacterial genus is distributed worldwide, even in extreme environments.