A type III polyketide synthase cluster in the phylum Planctomycetota is involved in alkylresorcinol biosynthesis.

Members of the bacterial phylum Planctomycetota have recently emerged as promising and for the most part untapped sources of novel bioactive compounds. The characterization of more than 100 novel species in the last decade stimulated recent bioprospection studies that start to unveil the chemical repertoire of the phylum. In this study, we performed systematic bioinformatic analyses based on the genomes of all 131 described members of the current phylum focusing on the identification of type III polyketide synthase (PKS) genes. Type III PKSs are versatile enzymes involved in the biosynthesis of a wide array of structurally diverse natural products with potent biological activities. We identified 96 putative type III PKS genes of which 58 are encoded in an operon with genes encoding a putative oxidoreductase and a methyltransferase. Sequence similarities on protein level and the genetic organization of the operon point towards a functional link to the structurally related hierridins recently discovered in picocyanobacteria. The heterologous expression of planctomycetal type III PKS genes from strains belonging to different families in an engineered Corynebacterium glutamicum strain led to the biosynthesis of pentadecyl- and heptadecylresorcinols. Phenotypic assays performed with the heterologous producer strains and a constructed type III PKS gene deletion mutant suggest that the natural function of the identified compounds differs from that confirmed in other bacterial alkylresorcinol producers. KEY POINTS: • Planctomycetal type III polyketide synthases synthesize long-chain alkylresorcinols. • Phylogenetic analyses suggest an ecological link to picocyanobacterial hierridins. • Engineered C. glutamicum is suitable for an expression of planctomycete-derived genes.

Uncovering the biotechnological capacity of marine and brackish water Planctomycetota.

An appealing strategy for finding novel bioactive molecules in Nature consists in exploring underrepresented and -studied microorganisms. Here, we investigated the antimicrobial and tumoral anti-proliferative bioactivities of twenty-three marine and estuarine bacteria of the fascinating phylum Planctomycetota. This was achieved through extraction of compounds produced by the Planctomycetota cultured in oligotrophic medium followed by an antimicrobial screening against ten relevant human pathogens including Gram-positive and Gram-negative bacteria, and fungi. Cytotoxic effects of the extracts were also evaluated against five tumoral cell lines. Moderate to potent activities were obtained against Enterococcus faecalis, methicillin-sensitive and methicillin-resistant Staphylococcus aureus and vancomycin-sensitive and vancomycin-resistant Enterococcus faecium. Anti-fungal effects were observed against Trichophyton rubrum, Candida albicans and Aspergillus fumigatus. The highest cytotoxic effects were observed against human breast, pancreas and melanoma tumoral cell lines. Novipirellula caenicola and Rhodopirellula spp. strains displayed the widest spectrum of bioactivities while Rubinisphaera margarita ICM_H10T affected all Gram-positive bacteria tested. LC-HRMS analysis of the extracts did not reveal the presence of any known bioactive natural product, suggesting that the observed activities are most likely caused by novel molecules, that need identification. In summary, we expanded the scope of planctomycetal species investigated for bioactivities and demonstrated that various strains are promising sources of novel bioactive compounds, which reenforces the potential biotechnological prospects offered by Planctomycetota.

An Update on Novel Taxa and Revised Taxonomic Status of Bacteria (Including Members of the Phylum Planctomycetota) Isolated from Aquatic Host Species Described in 2018 to 2021.

Increased interest in farmed aquatic species, aquatic conservation measures, and microbial metabolic end-product utilization have translated into a need for awareness and recognition of novel microbial species and revisions to bacterial taxonomy. Because this need has largely been unmet, through a 4-year literature review, we present lists of novel and revised bacterial species (including members of the phylum Planctomycetota) derived from aquatic hosts that can serve as a baseline for future biennial summaries of taxonomic revisions in this field. Most new and revised taxa were noted within oxidase-positive and/or nonglucose fermentative Gram-negative bacilli, including members of the Tenacibaculum, Flavobacterium, and Vibrio genera. Valid and effectively published novel members of the Streptococcus, Erysipelothrix, and Photobacterium genera are additionally described from disease pathogenesis perspectives.

Investigation of tRNA-based relatedness within the Planctomycetes-Verrucomicrobia-Chlamydiae (PVC) superphylum: a comparative analysis.

The PVC superphylum is a diverse group of prokaryotes that require stringent growth conditions. RNA is a fascinating molecule to find evolutionary relatedness according to the RNA World Hypothesis. We conducted tRNA gene analysis to find evolutionary relationships in the PVC phyla. The analysis of genomic data (P = 9, V = 4, C = 8) revealed that the number of tRNA genes varied from 28 to 90 in Planctomycetes and Chlamydia, respectively. Verrucomicrobia has whole genomes and the longest scaffold (3 + 1), with tRNA genes ranging from 49 to 53 in whole genomes and 4 in the longest scaffold. Most tRNAs in the E. coli genome clustered with homologs, but approximately 43% clustered with tRNAs encoding different amino acids. Planctomyces, Akkermansia, Isosphaera, and Chlamydia were similar to E. coli tRNAs. In a phylum, tRNAs coding for different amino acids clustered at a range of 8 to 10%. Further analysis of these tRNAs showed sequence similarity with Cyanobacteria, Proteobacteria, Viridiplantae, Ascomycota and Basidiomycota (Eukaryota). This indicates the possibility of horizontal gene transfer or, otherwise, a different origin of tRNA in PVC bacteria. Hence, this work proves its importance for determining evolutionary relatedness and potentially identifying bacteria using tRNA. Thus, the analysis of these tRNAs indicates that primitive RNA may have served as the genetic material of LUCA before being replaced by DNA. A quantitative analysis is required to test these possibilities that relate the evolutionary significance of tRNA to the origin of life.

Aeoliella straminimaris sp. nov., a novel member of the phylum Planctomycetota with an unusual filamentous structure.

Organisms with distinctive biological features and cellular organization constitute the bacterial phylum Planctomycetota. In this study, we formally describe a novel isolate, strain ICT_H6.2T, isolated from sediment samples collected in the brackish environment of the Tagus River estuary (Portugal) using an iChip-based culturing technique. The 16S rRNA gene analysis placed this strain into the phylum Planctomycetota and family Lacipirellulaceae, with a similarity value of 98.0 % to its closest relative Aeoliella mucimassa Pan181T, the currently only known member of the genus. Strain ICT_H6.2T has a genome size of 7.8 Mbp and a DNA G+C content of 59.6 mol %. Strain ICT_H6.2T is heterotrophic, aerobic and capable of microaerobic growth. This strain grows from 10 to 37 °C and from pH 6.5 to 10.0, requires salt to grow, and can tolerate up to 4 % (w/v) NaCl. Diverse nitrogen and carbon sources are utilized for growth. Morphologically, strain ICT_H6.2T is white to beige pigmented, spherical to ovoid in shape and around 1.4×1.1 µm in size. The strain clusters mainly in aggregates and younger cells show motility. Ultrastructural studies showed a cell plan with cytoplasmatic membrane invaginations and unusual filamentous structures with hexagonal organization in transversal section. Morphological, physiological and genomic comparison between strain ICT_H6.2T and its closest relatives strongly suggests it represents a novel species within the genus Aeoliella, for which we propose the name Aeoliella straminimaris sp. nov., represented by strain ICT_H6.2T as the type strain (=CECT 30574T=DSM 114064T).

Stieleria tagensis sp. nov., a novel member of the phylum Planctomycetota isolated from Tagus River in Portugal.

A bacterial strain was isolated from a brackish water sample of Tagus river, Alcochete, Portugal and was designated TO1_6T. It forms light pink colonies on M13 medium supplemented with N-acetylglucosamine. Cells are pear-shaped to spherical, form rosettes and divide by budding. Strain TO1_6T presents a mesophilic and neutrophilic profile, with optimum growth at 20 to 25 °C and pH 7.0 to 7.5, and vitamin supplementation is not required to promote its growth. The genome of the novel isolate is 7.77 Mbp in size and has a DNA G + C content of 56.3%. Based on its 16S rRNA gene sequence, this strain is affiliated with the phylum Planctomycetota. Further taxonomic characterization using additional phylogenetic markers, namely rpoB gene sequence (encoding the ß-subunit of the DNA-dependent RNA polymerase), as well as Percentage of conserved proteins, average nucleotide identity and average amino acid identity, suggest the affiliation of strain TO1_6T to the genus Stieleria, a recently described taxon in the family Pirellulaceae, order Pirellulales and class Planctomycetia. Based on the genotypic, phylogenetic and physiological characterization, we here describe a new species represented by the type strain TO1_6T (= CECT 30432T, = LMG 32465T), for which the name Stieleria tagensis sp. nov. is proposed.

Gemmata algarum, a Novel Planctomycete Isolated from an Algal Mat, Displays Antimicrobial Activity.

Axenic cultures of two strains, JC673T and JC717, both belonging to the phylum Planctomycetota, were isolated from distinct geographical locations in India. Strain JC673T was obtained from algal mats of a wetland situated in the state of Kerala, India, while strain JC717 originated from the Central Marine Fisheries Research Institute (CMFRI), state of Tamil Nadu, India. The two strains share 99.9% 16S rRNA gene sequence similarity and are most closely related to Gemmata obscuriglobus UQM 2246T (99.3% 16S rRNA gene sequence identity). The newly isolated strains are Gram-negative, grow aerobically and tolerate up to 4% (w/v) NaCl and a pH of up to 9.0. Cells are spherical and form pink-pigmented colonies. The respiratory quinone is MK-6. Major fatty acids are C18:0, C16:1ω5c and C16:0. Polar lipids include phosphatidylcholine, phosphatidylethanolamine, several unidentified amino lipids, unidentified phospholipids, additional unidentified lipids, and an unidentified choline lipid. The polyamine spermidine is produced by the two strains. The strains have a genome size of about 8.2 Mb with a DNA G+C content of 67.6%. Solvent-based culture extracts of the isolates showed antimicrobial activity against three bacterial test strains. Their phylogenetic position along with differences in morphological, physiological, and genomic features support the classification as a new species of the genus Gemmata, for which we propose the name Gemmata algarum sp. nov. Strain JC673T (=KCTC 72851T = NBRC 114340T) and JC717 are the type and non-type strain of the new species, respectively.

Dynamics in an unusual acyl carrier protein from a ladderane lipid-synthesizing organism.

Anaerobic ammonium-oxidizing (anammox) bacteria express a distinct acyl carrier protein implicated in the biosynthesis of the highly unusual "ladderane" lipids these organisms produce. This "anammox-specific" ACP, or amxACP, shows several unique features such as a conserved FF motif and an unusual sequence in the functionally important helix III. Investigation of the protein's structure and dynamics, both in the crystal by ensemble refinement and by MD simulations, reveals that helix III adopts a rare six-residue-long 310 -helical conformation that confers a large degree of conformational and positional variability on this part of the protein. This way of introducing structural flexibility by using the inherent properties of 310 -helices appears unique among ACPs. Moreover, the structure suggests a role for the FF motif in shielding the thioester linkage between the protein's prosthetic group and its acyl cargo from hydrolysis.

Reconciling Asgardarchaeota Phylogenetic Proximity to Eukaryotes and Planctomycetes Cellular Features in the Evolution of Life.

The relationship between the three domains of life-Archaea, Bacteria, and Eukarya-is one of Biology's greatest mysteries. Current favored models imply two ancestral domains, Bacteria and Archaea, with eukaryotes originating within Archaea. This type of models has been supported by the recent description of the Asgardarchaeota, the closest prokaryotic relatives of eukaryotes. However, there are many problems associated with any scenarios implying that eukaryotes originated from within the Archaea, including genome mosaicism, phylogenies, the cellular organization of the Archaea, and their ancestral character. By contrast, all models of eukaryogenesis fail to consider two relevant discoveries: the detection of membrane coat proteins, and of phagocytosis-related processes in Planctomycetes, which are among the bacteria with the most developed endomembrane system. Consideration of these often overlooked features and others found in Planctomycetes and related bacteria suggest an evolutionary model based on a single ancestral domain. In this model, the proximity of Asgard and eukaryotes is not rejected but instead, Asgard are considered as diverging away from a common ancestor instead of on the way toward the eukaryotic ancestor. This model based on a single ancestral domain solves most of the ambiguities associated with the ones based on two ancestral domains. The single-domain model is better suited to explain the origin and evolution of all three domains of life, blurring the distinctions between them. Support for this model as well as the opportunities that it presents not only for reinterpreting previous results, but also for planning future experiments, are explored.

Functional diversity of isoprenoid lipids in Methylobacterium extorquens PA1.

Hopanoids and carotenoids are two of the major isoprenoid-derived lipid classes in prokaryotes that have been proposed to have similar membrane ordering properties as sterols. Methylobacterium extorquens contains hopanoids and carotenoids in their outer membrane, making them an ideal system to investigate the role of isoprenoid lipids in surface membrane function and cellular fitness. By genetically knocking out hpnE and crtB we disrupted the production of squalene and phytoene in M. extorquens PA1, which are the presumed precursors for hopanoids and carotenoids respectively. Deletion of hpnE revealed that carotenoid biosynthesis utilizes squalene as a precursor resulting in pigmentation with a C30 backbone, rather than the previously predicted canonical C40 phytoene-derived pathway. Phylogenetic analysis suggested that M. extorquens may have acquired the C30 pathway through lateral gene transfer from Planctomycetes. Surprisingly, disruption of carotenoid synthesis did not generate any major growth or membrane biophysical phenotypes, but slightly increased sensitivity to oxidative stress. We further demonstrated that hopanoids but not carotenoids are essential for growth at higher temperatures, membrane permeability and tolerance of low divalent cation concentrations. These observations show that hopanoids and carotenoids serve diverse roles in the outer membrane of M. extorquens PA1.

Targeted metagenome sequencing reveals the abundance of Planctomycetes and Bacteroidetes in the rhizosphere of pomegranate.

Agricultural productivity of pomegranate can be enhanced by identifying the crop-associated microbial diversity in the rhizosphere region with respect to plant growth promoters and other beneficial organisms. Traditional culture methods have limitations in microbial screening as only 1-2% of these organisms can be cultured. In the present study, 16S rRNA amplicon-based metagenomics approach using MinION Oxford Nanopore platform was employed to explore the microbial diversity in the rhizosphere of pomegranate Bhagwa variety, across variable soil depths from 0 to 5 cms (R2), 5-10 cms (R4) and 10-15 cms (R6), using bulk soil as the control. Across all the three layers, significant variations in pH, nitrogen content and total fungal count were observed. 16S rRNA analysis showed the abundance of planctomycetes, Pirellula staleyi, followed by bacteroidetes, Flavisolibacter LC59 and Niastella koreensis across the various soil depths in the rhizospheric soil samples. Pathway prediction analysis indicated arginine and proline metabolism (gamma-glutamyl putrescine oxidase) and hydrogen sulfide biosynthesis as the most abundant pathway hits. Comparative abundance analysis across layers showed the R6 layer with the maximum microbial diversity in terms of highest dimension of variation (79.2%) followed by R4 and R2 layers (p < 0.01). Our analysis shows the significant influence of root zone in shaping microbial diversity. This study has reported the presence of Planctomycetes, Pirellula staleyi for the first time in the pomegranate field.

The Planctomycetia: an overview of the currently largest class within the phylum Planctomycetes.

The phylum Planctomycetes comprises bacteria with uncommon features among prokaryotes, such as cell division by budding, absence of the bacterial tubulin-homolog cell division protein FtsZ and complex cell plans with invaginations of the cytoplasmic membrane. Although planctomycetes are ubiquitous, the number of described species and isolated strains available as axenic cultures is still low compared to the diversity observed in metagenomes or environmental studies. An increasing interest in planctomycetes is reflected by the recent description of a large number of new species and their increasing accessibility in terms of pure cultures. In this review, data from all taxonomically described species belonging to Planctomycetia, the class with the currently highest number of characterized members within the phylum Planctomycetes, is summarized. Phylogeny, morphology, physiology, ecology and genomic traits of its members are discussed. This comprehensive overview will help to acknowledge several aspects of the biology of these fascinating bacteria.

Mucisphaera calidilacus gen. nov., sp. nov., a novel planctomycete of the class Phycisphaerae isolated in the shallow sea hydrothermal system of the Lipari Islands.

For extending the current collection of axenic cultures of planctomycetes, we describe in this study the isolation and characterisation of strain Pan265T obtained from a red biofilm in the hydrothermal vent system close to the Lipari Islands in the Tyrrhenian Sea, north of Sicily, Italy. The strain forms light pink colonies on solid medium and grows as a viscous colloid in liquid culture, likely as the result of formation of a dense extracellular matrix observed during electron microscopy. Cells of the novel isolate are spherical, motile and divide by binary fission. Strain Pan265T is mesophilic (temperature optimum 30-33 °C), neutrophilic (pH optimum 7.0-8.0), aerobic and heterotrophic. The strain has a genome size of 3.49 Mb and a DNA G + C content of 63.9%. Phylogenetically, the strain belongs to the family Phycisphaeraceae, order Phycisphaerales, class Phycisphaerae. Our polyphasic analysis supports the delineation of strain Pan265T from the known genera in this family. Therefore, we conclude to assign strain Pan265T to a novel species within a novel genus, for which we propose the name Mucisphaera calidilacus gen. nov., sp. nov. The novel species is the type species of the novel genus and is represented by strain Pan265T (= DSM 100697T = CECT 30425T) as type strain.

Planktonic bacteria in white shrimp (Litopenaeus vannamei) and channel catfish (Letalurus punetaus) aquaculture ponds in a salt-alkaline region.

Aquaculture in salt-alkaline regions is encouraged in China, and culture of many aquatic species has been introduced into these areas. In this study, we cultured two species, white shrimp (Litopenaeus vannamei) and channel catfish (Letalurus punetaus) separately in aquaculture ponds in a salt-alkaline region in northwest China and assessed the impacts of the aquaculture operations on the planktonic bacterial community in the culture ponds. Culture of both species decreased the planktonic bacterial diversity and altered the bacterial community structure in the aquaculture ponds compared with the source water. Among the 10 dominant bacterial phyla, 8 were significantly correlated with environmental parameters; the exception was Actinobacteriota, the most dominant phylum, and Firmicutes. Proteobacteria and Bacteroidota abundances showed significant positive correlations with alkalinity, whereas Patescibacteria, Cyanobacteria, Planctomycetota, and Verrucomicrobiota abundance were positively correlated with salinity. Linear regression analysis showed that alkalinity was positively correlated with bacterial beta diversity and salinity was negatively correlated with that. In addition, white shrimp aquaculture significantly lowered the alkalinity, which suggests that culture of this species in inland salt-alkaline regions is a potential dealkalization solution.

Anammox biofilter with denitrification sludge as seed in treating low nitrogen strength wastewater.

Deficient seed sludge, low substrate concentrations are recognized as the major barriers for the application of anaerobic ammonia oxidation (Anammox) to treat mainstream wastewater. In this work, anammox biofilter (A-BF) was started up by inoculating denitrification sludge at low nitrogen strength at 25 °C. The total nitrogen removal efficiency (TNRE) and nitrogen removal rate (NRR) reached 74.8 ± 3.4% and 0.81 kg-N m-3 d-1 under nitrogen loading rate (NLR) of 1.20 kg-N m-3 d-1 with 7.00 mg-NH4+-N L-1 and 10.00 mg-NO2--N L-1 as influent. 1.00-2.00 mg-DO L-1 negatively impacted effluent, but the total nitrogen of effluent (TNeff) was 10.65 ± 2.76 mg L-1, in limit of the standard of Class 1A for municipal WWTP discharge (GB18918-2002). The abundance of Planctomycetes increased from 0.6% to 1.4-2.6%, in which, Candidatus_Brocadia was the dominant genera. The results establish the application feasibility of A-BFs as advanced nitrogen removal technique in treating mainstream wastewater.

Bamboo charcoal addition enhanced the nitrogen removal of anammox granular sludge with COD: Performance, physicochemical characteristics and microbial community.

The effects of different chemical oxygen demand (COD) concentrations on the anammox granular sludge with Bamboo Charcoal (BC) addition were evaluated in UASB reactor. The results showed that the average total nitrogen (TN) removal efficiency was reduced from 85.9% to 81.4% when COD concentration was increased from 50 to 150 mg/L. However, the TN removal efficiency of BC addition reactors was dramatically 3.1%-6.4% higher than that without BC under different COD concentrations. The average diameter of granular sludge was 0.13 mm higher than that without BC. The settling velocity was increased by elevated COD concentration, while the EPS and VSS/SS were increased with BC addition. The high-throughput Miseq sequencing analyses revealed that the bacterial diversity and richness were decreased under COD addition, and the Planctomycetes related to anammox bacteria were Candidatus Brocadia and Candidatus Kuenenia. The Metagenomic sequencing indicated that the abundance of denitrification related functional genes all increased with elevated COD, while the abundance of anammox related functional genes of decreased. The functional genes related to anammox was hydrazine synthase encoding genes (hzsA, hzsB and hzsB). The average relative abundance of hzs genes in the reactor with BC addition was higher than the control at COD concentrations of 50 mg/L and 150 mg/L. The functional genes of denitrification mediated by BC were higher than those without BC throughout the operation phase. It is interesting to note that BC addition greatly enriched the related functional genes of denitrification and anammox.

Wide distribution of Phycisphaera-like planctomycetes from WD2101 soil group in peatlands and genome analysis of the first cultivated representative.

Phycisphaera-like WD2101 'soil group' is one of the as-yet-uncultivated phylogenetic clades within the phylum Planctomycetes. Members of this clade are commonly detected in various terrestrial habitats. This study shows that WD2101 represented one of the major planctomycete groups in 10 boreal peatlands, comprising up to 76% and 36% of all Planctomycetes-affiliated 16S rRNA gene reads in raised bogs and eutrophic fens respectively. These types of peatlands displayed clearly distinct intra-group diversity of WD2101-affiliated planctomycetes. The first isolate of this enigmatic planctomycete group, strain M1803, was obtained from a humic lake surrounded by Sphagnum peat bogs. Strain M1803 displayed 89.2% 16S rRNA gene similarity to Tepidisphaera mucosa and was represented by motile cocci that divided by binary fission and grew under micro-oxic conditions. The complete 7.19 Mb genome of strain M1803 contained an array of genes encoding Planctomycetal type bacterial microcompartment organelle likely involved in l-rhamnose metabolism, suggesting participation of M1803-like planctomycetes in polysaccharide degradation in peatlands. The corresponding cellular microcompartments were revealed in ultrathin cell sections. Strain M1803 was classified as a novel genus and species, Humisphaera borealis gen. nov., sp. nov., affiliated with the formerly recognized WD2101 'soil group'.

High Salinity Inhibits Soil Bacterial Community Mediating Nitrogen Cycling.

Salinization is considered a major threat to soil fertility and agricultural productivity throughout the world. Soil microbes play a crucial role in maintaining ecosystem stability and function (e.g., nitrogen cycling). However, the response of bacterial community composition and community-level function to soil salinity remains uncertain. Here, we used multiple statistical analyses to assess the effect of high salinity on bacterial community composition and potential metabolism function in the agricultural ecosystem. Results showed that high salinity significantly altered both bacterial alpha (Shannon-Wiener index and phylogenetic diversity) and beta diversity. Salinity, total nitrogen (TN), and soil organic matter (SOM) were the vital environmental factors shaping bacterial community composition. The relative abundance of Actinobacteria, Chloroflexi, Acidobacteria, and Planctomycetes decreased with salinity, whereas Proteobacteria and Bacteroidetes increased with salinity. The modularity and the ratio of negative to positive links remarkedly decreased, indicating that high salinity destabilized bacterial networks. Variable selection, which belongs to deterministic processes, mediated bacterial community assembly within the saline soils. Function prediction results showed that the key nitrogen metabolism (e.g., ammonification, nitrogen fixation, nitrification, and denitrification processes) was inhibited in high salinity habitats. MiSeq sequencing of 16S rRNA genes revealed that the abundance and composition of the nitrifying community were influenced by high salinity. The consistency of function prediction and experimental verification demonstrated that high salinity inhibited soil bacterial community mediating nitrogen cycling. Our study provides strong evidence for a salinity effect on the bacterial community composition and key metabolism function, which could help us understand how soil microbes respond to ongoing environment perturbation. IMPORTANCE Revealing the response of the soil bacterial community to external environmental disturbances is an important but poorly understood topic in microbial ecology. In this study, we evaluated the effect of high salinity on the bacterial community composition and key biogeochemical processes in salinized agricultural soils (0.22 to 19.98 dS m-1). Our results showed that high salinity significantly decreased bacterial diversity, altered bacterial community composition, and destabilized the bacterial network. Moreover, variable selection (61% to 66%) mediated bacterial community assembly within the saline soils. Functional prediction combined with microbiological verification proved that high salinity inhibited soil bacterial community mediating nitrogen turnover. Understanding the impact of salinity on soil bacterial community is of great significance for managing saline soils and maintaining a healthy ecosystem.

Aquisphaera insulae sp. nov., a new member in the family Isosphaeraceae, isolated from the floating island of Loktak lake and emended description of the genus Aquisphaera.

Strain JC669T was isolated from a floating island of Loktak lake, Manipur, India and shares the highest 16S rRNA gene sequence identity with Aquisphaera giovannonii OJF2T. The novel strain is aerobic, Gram negative, light pink-coloured, non-motile, NaCl intolerant and spherical to oval-shaped. It grows in the form of single cells or aggregates and possibly forms structures which appear like fruiting bodies. Strain JC669T grows well up to pH 9.0.The isolate produces MK-6 as respiratory quinone, C18:1ω9c, C16:0 and C18:0 as major fatty acids and phosphatidylcholine, an unidentified amino lipid, an unidentified choline lipid (UCL) and six additional unidentified lipids (UL1, 2, 3, 4, 5, 6) as polar lipids. Strain JC669T has a large genome size of 10.04 Mb and the genomic G + C content was 68.5 mol%. The genome contained all genes essential for lycopene related carotenoid biosynthesis. The polyphasic analysis of its phylogenetic position, morphological, physiological and genomic features supports the classification of strain JC669T as a novel species of the genus Aquisphaera, for which we propose the name Aquisphaera insulae sp. nov. Strain JC669T (= KCTC 72672T = NBRC 114306T) is the type strain of the novel species.

Heterologous Expression of Thermogutta terrifontis Endo-Xanthanase in Penicillium verruculosum, Isolation and Primary Characterization of the Enzyme.

Heterologous endo-xanthanase (EX) from the thermophilic planktomycete Thermogutta terrifontis strain was obtained using Penicillium verruculosum 537 (ΔniaD) expression system with the cellobiohydrolase 1 gene promoter. Homogeneous EX with a molecular weight of 23.7 kDa (pI 6.5) was isolated using liquid chromatography methods. This xanthan degrading enzyme also possesses the enzymatic activity towards CM-cellulose, ß-glucan, curdlan, lichenan, laminarin, galactomannan, xyloglucan but not towards p-nitrophenyl derivatives of ß-D-glucose, mannose and cellobiose. The temperature and pH optima of EX were 55°C and 4.0, respectively; the enzyme exhibited 90% of its maximum activity in the temperature range 50-60°C and pH 3-5.