Alkalicoccobacillus porphyridii sp. nov., isolated from a marine red alga, reclassification of Shouchella plakortidis and Shouchella gibsonii as Alkalicoccobacillus plakortidis comb. nov. and Alkalicoccobacillus gibsonii comb. nov., and emended description of the genus Alkalicoccobacillus Joshi et al. 2022

Genomic insights into novel extremotolerant bacteria isolated from the NASA Phoenix mission spacecraft assembly cleanrooms

BACKGROUND

Human-designed oligotrophic environments, such as cleanrooms, harbor unique microbial communities shaped by selective pressures like temperature, humidity, nutrient availability, cleaning reagents, and radiation. Maintaining the biological cleanliness of NASA's mission-associated cleanrooms, where spacecraft are assembled and tested, is critical for planetary protection. Even with stringent controls such as regulated airflow, temperature management, and rigorous cleaning, resilient microorganisms can persist in these environments, posing potential risks for space missions.

RESULTS

During the Phoenix spacecraft mission, genomes of 215 bacterial isolates were sequenced and based on overall genome-related indices, 53 strains belonging to 26 novel species were recognized. Metagenome mapping indicated less than 0.1% of the reads associated with novel species, suggesting their rarity. Genes responsible for biofilm formation, such as BolA (COG0271) and CvpA (COG1286), were predominantly found in proteobacterial members but were absent in other non-spore-forming and spore-forming species. YqgA (COG1811) was detected in most spore-forming members but was absent in Paenibacillus and non-spore-forming species. Cell fate regulators, COG1774 (YaaT), COG3679 (YlbF, YheA/YmcA), and COG4550 (YmcA, YheA/YmcA), controlling sporulation, competence, and biofilm development processes, were observed in all spore-formers but were missing in non-spore-forming species. COG analyses further revealed resistance-conferring proteins in all spore-formers (n = 13 species) and eight actinobacterial species, responsible for enhanced membrane transport and signaling under radiation (COG3253), transcription regulation under radiation stress (COG1108), and DNA repair and stress responses (COG2318). Additional functional analysis revealed that Agrococcus phoenicis, Microbacterium canaveralium, and Microbacterium jpeli contained biosynthetic gene clusters (BGCs) for ε-poly-L-lysine, beneficial in food preservation and biomedical applications. Two novel Sphingomonas species exhibited for zeaxanthin, an antioxidant beneficial for eye health. Paenibacillus canaveralius harbored genes for bacillibactin, crucial for iron acquisition. Georgenia phoenicis had BGCs for alkylresorcinols, compounds with antimicrobial and anticancer properties used in food preservation and pharmaceuticals.

CONCLUSION

Despite stringent decontamination and controlled environmental conditions, cleanrooms harbor unique bacterial species that form biofilms, resist various stressors, and produce valuable biotechnological compounds. The reduced microbial competition in these environments enhances the discovery of novel microbial diversity, contributing to the mitigation of microbial contamination and fostering biotechnological innovation. Video Abstract.

An update on novel taxa and revised taxonomic status of bacteria isolated from aquatic host species described in 2022-2023

The description of new taxa and nomenclature updates to currently known taxa from aquatic animal species continues. After a review of the literature from 2022 and 2023, multiple lists of bacteria, including members of Phylum Planctomycetota, were compiled. As with the previous review, most bacteria are oxidase-positive Gram-negative bacilli with familiar families including new taxa in Aeromonadaceae, Flavobacteriaceae, and Vibrionaceae. A number of Gram-positive bacilli are described including new taxa in the Nocardioides, Paenibacillus, and Streptomyces genera. Two anaerobic species are listed, and one new member of Family Planctomycetaceae is noted. Revised taxa are briefly mentioned. The majority of new and revised taxa are isolated from healthy aquatic animals, and therefore, the role of these new bacteria in health and disease is unknown. Bacteria with pathogenic association and potential production of bioactive substances are highlighted.

Marinomonas rhodophyticola sp. nov. and Marinomonas phaeophyticola sp. nov., isolated from marine algae

Two Gram-stain-negative, facultatively aerobic, and motile rod bacteria, designated as strains KJ51-3T and 15G1-11T, were isolated from marine algae collected in the Republic of Korea. Both strains exhibited catalase- and oxidase-positive activities. Optimum growth conditions for strain KJ51-3T were observed at 30 °C and pH 6.0-8.0, with 1.0-7.0 % (w/v) NaCl, whereas strain 15G1-11T exhibited optimal growth at 30 °C, pH 7.0, and 1.0-5.0 % NaCl. Major fatty acids detected in both strains included C16 : 0, C10 : 0 3-OH and summed features 3 (C16 : 1  ω7c and/or C16 : 1  ω6c) and 8 (C18 : 1  ω7c and/or C18 : 1  ω6c). As for polar lipids, strain KJ51-3T contained phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol, and two unidentified phospholipids, whereas strain 15G1-11T had PE, PG, and an unidentified aminolipid. Ubiquinone-8 was the predominant respiratory quinone in both strains, with minor detection of ubiquinone-9 in strain KJ51-3T. The genomic DNA G+C contents were 44.0 mol% for strain KJ51-3T and 40.5 mol% for strain 15G1-11T. Phylogenetic analyses based on both 16S rRNA gene and genome sequences placed strains KJ51-3T and 15G1-11T into distinct lineages within the genus Marinomonas, most closely related to Marinomonas arctica 328T (98.6 %) and Marinomonas algicola SM1966T (98.3 %), respectively. Strains KJ51-3T and 15G1-11T exhibited a 94.6 % 16S rRNA gene sequence similarity and a 70.7 % average nucleotide identity (ANI), with ANI values of 91.9 and 79.3 % between them and M. arctica 328T and M. algicola SM1966T, respectively, indicating that they represent novel species. In summary, based on their phenotypic, chemotaxonomic, and phylogenetic properties, strains KJ51-3T and 15G1-11T are proposed to represent novel species within the genus Marinomonas, for which the names Marinomonas rhodophyticola sp. nov. (KJ51-3T=KACC 22756T=JCM 35591T) and Marinomonas phaeophyticola sp. nov. (15G1-11T=KACC 22593T=JCM 35412T) are respectively proposed.

Coraliomargarita algicola sp. nov., isolated from a marine green alga

A Gram-stain-negative, facultative aerobic, catalase- and oxidase-positive, non-motile, non-flagellated, and coccus-shaped bacterium, strain J2-16T, isolated from a marine green alga, was characterized taxonomically. Strain J2-16T grew at 20-40 °C (optimum, 30 °C), pH 6.0-10.0 (optimum, pH 7.0), and 1.0-4.0 % (w/v) NaCl (optimum, 3.0 %). Menaquinone-7 was identified as the sole respiratory quinone, and major fatty acids (>5 %) were C18 : 1  ω9c, iso-C14 : 0, C14 : 0, anteiso-C15 : 0, C18 : 0, C16 : 0, and C17 : 1  ω8c. The polar lipids of strain J2-16T consisted of phosphatidylglycerol, phosphatidylethanolamine, two unidentified phospholipids, and three unidentified lipids. The genome size of strain J2-16T was 5384 kb with a G+C content of 52.0 mol%. Phylogenetic analyses based on 16S rRNA gene and 120 protein marker sequences revealed that strain J2-16T formed a distinct phyletic lineage within the genus Coraliomargarita, closely related to Coraliomargarita sinensis WN38T and Coraliomargarita akajimensis DSM 45221T with 16S rRNA gene sequence similarities of 95.7 and 94.4 %, respectively. Average nucleotide identity and digital DNA-DNA hybridization values between strain J2-16T and Coraliomargarita species were lower than 71.2 and 20.0 %, respectively. The phenotypic, chemotaxonomic, and molecular features support that strain J2-16T represents a novel species of the genus Coraliomargarita, for which the name Coraliomargarita algicola sp. nov. is proposed. The type strain is J2-16T (=KACC 22590T=JCM 35407T).

Roseibium algicola sp. nov. and Roseibium porphyridii sp. nov., isolated from marine red algae

Two Gram-stain-negative, strictly aerobic rods, designated as RMAR6-6T and KMA01T, exhibiting catalase- and oxidase-positive activities, were isolated from marine red algae in the Republic of Korea. Cells of strain RMAR6-6T exhibited flagellar motility, while those of strain KMA01T were non-motile. Strain RMAR6-6T exhibited optimal growth at 30-35°C and pH 7.0-8.0 with 4.0-6.0 % (w/v) NaCl, while strain KMA01T grew optimally at 30-35 °C, pH 7.0-8.0 and 2.0-5.0% NaCl. Both strains shared common major respiratory isoprenoid quinone (ubiquinone-10), cellular fatty acids (C18 : 0, C18: 1  ω7c 11-methyl, C20 : 1  ω7c and summed feature 8) and polar lipids (phosphatidylglycerol, phosphatidylmonomethylethanolamine, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and sulphoquinovosyldiacylglycerol). The genomic DNA G+C contents were 59.0 and 55.0 mol% for strains RMAR6-6T and KMA01T, respectively. With 98.5 % 16S rRNA gene similarity, 75.2 % average nucleotide identity (ANI) and 19.8 % digital DNA-DNA hybridization (dDDH) values, strains RMAR6-6T and KMA01T were identified as representing distinct species. Phylogenetic analyses based on both 16S rRNA gene and genome sequences revealed that strains RMAR6-6T and KMA01T formed distinct phylogenic lineages within the genus Roseibium, most closely related to Roseibium aggregatum IAM 12614T and Roseibium album CECT 5094T, respectively. The ANI and dDDH values between strain RMAR6-6T and R. aggregatum IAM 12614T were 87.5 and 33.3 %, respectively. Similarly, the values between KMA01T and R. album CECT 5094T were 74.2 % (ANI) and 19.3 % (dDDH). Based on phenotypic, chemotaxonomic and molecular characteristics, strains RMAR6-6T and KMA01T represent two novel species of the genus Roseibium, for which the names R. algicola sp. nov. (RMAR6-6T=KACC 22482T=JCM 34977T) and R. porphyridii sp. nov. (KMA01T=KACC 22479T=JCM 34597T) are proposed, respectively.