Zooshikella harenae sp. nov., Isolated from Pacific Oyster Crassostrea gigas, and Establishment of Zooshikella ganghwensis subsp. marina subsp. nov. and Zooshikella ganghwensis subsp. ganghwensis subsp. nov.

A critical reduction in discovering new antimicrobial compounds has driven us to search for rare antibiotic-producing species from underexplored habitats like the sea [1]. Microbiologists, pharmacologists, and biochemists have developed an interest in the marine environment in order to harvest water-soluble bacterial pigments. With the recent growth in awareness of the advantages of natural versus synthetic goods, the worldwide market for bio-pigments is projected to grow [2]. The analysis of a potential natural ecosystem is the first and most significant stage in locating an environment that may accommodate a wide range of bio-pigment sources. The marine environment is home to over 80% of all living organisms [3]. It is a rich source of aquatic microbial organisms with a wider variety than their telluric equivalents [4]. The marine environment is now being touted as a promising source of bio-pigment [5]. Many microorganisms from such biotopes have previously been studied for pigment synthesis. At the same time, a large number of them are used for different industrial applications [4]. The capacity of marine microbes to create colors in harsh settings, such as very acidic/alkaline environments (pH 4 and >9), extreme temperatures (2–15 C and 60–110 °C), and restricted substrate supply, determines their choice [6,7]. In this study, we report the polyphasic taxonomy of a novel isolate from the genus Zooshikella from the sand sediment located between the lumen of the Crassostrea gigas. The genus Zooshikella belongs to Gram-negative bacteria, which are characterised as aerobic, chemo-organotrophic, and halophilic bacteria in the family Zooshikellaceae (which previously was in the family Hahellaceae) [8,9]. Prodigiosin and cycloprodigiosin are two members of secondary metabolites for Zooshikella sp. [9,10,11]. Many bacteria, including Serratia marcescens, Hahella chejuensis, Streptomyces variegatus, Colwellia (Vibrio) psychrerythraea, Pseudomonas magnesiorubera, and other eubacteria, produce prodigiosin (PDG) [12]. Prodigiosin belongs to the prodiginine community, which is made up of structural isomers with a tripyrrole center and various alkyl chains. This compound has significant biological potential because of its antimicrobial [13], antimalarial [14], anticancer [15], and immunosuppressive properties [16]. According to a recent study, prodigiosin or its analogues were recently found to be successful biological control agents against harmful algae [17,18]. They could also be used as a natural dye [19] and are classified as cell growth regulators [20]. On the other hand, cycloprodigiosin (cPDG) is only produced in trace amounts by a few marine bacteria, such as Pseudoalteromonas (Alteromonas) rubra, Pseudoalteromonas denitrificans, and Vibrio gazogenes [21,22,23]. Cycloprodigiosin hydrochloride has demonstrated potent anticancer activity against various cancer cell lines, implying that cPDG may belong to a new anticancer drug class [12,24,25,26]. At the moment of writing, the family of Zooshikellaceae is comprised of genera Endozoicomonas, Kistimonas, Parendozoicomonas, and Zooshikella. Zooshikella includes only two species with validly published names as Zooshikella ganghwensis and Zooshikella marina [9,11]. Zooshikella rubidus S1-1 has been effectively published [10], but its species name remains to obtain approval.