Classification of a Violacein-Producing Psychrophilic Group of Isolates Associated with Freshwater in Antarctica and Description of Rugamonas violacea sp. nov

Natural Pigments Production and Their Application in Food, Health and Other Industries

In addition to fulfilling their function of giving color, many natural pigments are known as interesting bioactive compounds with potential health benefits. These compounds have various applications. In recent times, in the food industry, there has been a spread of natural pigment application in many fields, such as pharmacology and toxicology, in the textile and printing industry and in the dairy and fish industry, with almost all major natural pigment classes being used in at least one sector of the food industry. In this scenario, the cost-effective benefits for the industry will be welcome, but they will be obscured by the benefits for people. Obtaining easily usable, non-toxic, eco-sustainable, cheap and biodegradable pigments represents the future in which researchers should invest.

Duganella vulcania sp. nov., Rugamonas fusca sp. nov., Rugamonas brunnea sp. nov. and Rugamonas apoptosis sp. nov., isolated from subtropical streams, and phylogenomic analyses of the genera Janthinobacterium, Duganella, Rugamonas, Pseudoduganella and Massilia

Six Gram-stain-negative, catalase- and oxidase-positive, rod-shaped and motile strains (FT81WT, FT82W, FT107W, FT3ST, LX20WT and LX47WT) sharing high 16S rRNA gene sequence similarities with species of the genera Janthinobacterium (97.0–98.3 %), Duganella (96.3–98.8 %), Rugamonas (97.8–98.6 %), Pseudoduganella (96.8–97.5 %) and Massilia (94.5–98.6 %) were isolated from subtropical streams in PR China. The phylogenetic trees reconstructed using the 16S rRNA gene sequences indicated that the species of above five genera often mix together, indicating that the taxonomic statuses of some species were questionable. Phylogenomic reconstruction based on 369 single-copy orthologous clusters indicated that the species of the genus Janthinobacterium form a distinct cluster, strains FT81WT, FT82W and FT107W form a tight cluster with the species of the genus Duganella , and strains FT3ST, LX20WT and LX47WT form a tight cluster with the species of genus Rugamonas , and the species of genus Pseudoduganella form a tight cluster with Massilia guangdongensis , Massilia ginsengisoli , Massilia rivuli , Massilia namucuonensis , Massilia aquatica sensu Lu et al., Massilia buxea , Massilia armeniaca , Massilia plicata , Massilia flava , Massilia lurida , Massilia dura , Massilia lutea , Massilia umbonata , Massilia albidiflava and Massilia violacea . It should be noted that Massilia aquatica Lu et al. 2020 non Massilia aquatica Holochová et al. 2020 is a later homonym and an illegitimate name. The GTDB Release 202 also supported the proposal that M. guangdongensis , M. ginsengisoli , M. rivuli , M. namucuonensis , M. aquatica sensu Lu et al., M. buxea , M. armeniaca , M. plicata , M. flava , M. lurida , M. dura , M. lutea , M. umbonata , M. albidiflava and M. violacea should be transferred into the genus Pseudoduganella . The calculated pairwise orthologous average nucleotide identity by usearch (OrthoANIu) values were between 95.0 % and 95.6 % among strains FT81WT, FT82W and FT107W, but were less than 91.5 % among strains FT3ST, LX20WT, LX47WT and other related strains. Combining the results of phylogenomic analyses, phenotypic, biochemical and genotypic characteristics, strains FT81WT, FT82W and FT107W should represent a novel species of the genus Duganella , and strains FT3ST, LX20WT and LX47WT should represent three novel species of the genus Rugamonas , for which the names Duganella vulcania sp. nov. (type strain FT81WT=GDMCC 1.1679T =KACC 21471T), Rugamonas fusca sp. nov. (type strain FT3ST=GDMCC 1.1907T =KACC 21952T), Rugamonas brunnea sp. nov. (type strain LX20WT=GDMCC 1.1911T =KACC 21956T) and Rugamonas apoptosis sp. nov. (type strain LX47WT=GDMCC 1.1914T =KACC 21959T) are proposed.

Characterisation of Waterborne Psychrophilic Massilia Isolates with Violacein Production and Description of Massilia antarctica sp. nov

A group of seven bacterial strains producing blue-purple pigmented colonies on R2A agar was isolated from freshwater samples collected in a deglaciated part of James Ross Island and Eagle Island, Antarctica, from 2017–2019. The isolates were psychrophilic, oligotrophic, resistant to chloramphenicol, and exhibited strong hydrolytic activities. To clarify the taxonomic position of these isolates, a polyphasic taxonomic approach was applied based on sequencing of the 16S rRNA, gyrB and lepA genes, whole-genome sequencing, rep-PCR, MALDI-TOF MS, chemotaxonomy analyses and biotyping. Phylogenetic analysis of the 16S rRNA gene sequences revealed that the entire group are representatives of the genus Massilia. The closest relatives of the reference strain P8398T were Massilia atriviolacea, Massilia violaceinigra, Massilia rubra, Massilia mucilaginosa, Massilia aquatica, Massilia frigida, Massilia glaciei and Massilia eurypsychrophila with a pairwise similarity of 98.6–100% in the 16S rRNA. The subsequent gyrB and lepA sequencing results showed the novelty of the analysed group, and the average nucleotide identity and digital DNA–DNA hybridisation values clearly proved that P8398T represents a distinct Massilia species. After all these results, we nominate a new species with the proposed name Massilia antarctica sp. nov. The type strain is P8398T (= CCM 8941T = LMG 32108T).