Dynamics of bacterial and archaeal communities during horse bedding and green waste composting

Organic waste decomposition can make up substantial amounts of municipal greenhouse emissions during decomposition. Composting has the potential to reduce these emissions as well as generate sustainable fertilizer. However, our understanding of how complex microbial communities change to drive the chemical and biological processes of composting is still limited. To investigate the microbiota associated with organic waste decomposition, initial composting feedstock (Litter), three composting windrows of 1.5 months (Young phase), 3 months (Middle phase) and 12 months (Aged phase) old, and 24-month-old mature Compost were sampled to assess physicochemical properties, plant cell wall composition and the microbial community using 16S rRNA gene amplification. A total of 2,612 Exact Sequence Variants (ESVs) included 517 annotated as putative species and 694 as genera which together captured 57.7% of the 3,133,873 sequences, with the most abundant species being Thermobifida fusca, Thermomonospora chromogena and Thermobifida bifida. Compost properties changed rapidly over time alongside the diversity of the compost community, which increased as composting progressed, and multivariate analysis indicated significant variation in community composition between each time-point. The abundance of bacteria in the feedstock is strongly correlated with the presence of organic matter and the abundance of plant cell wall components. Temperature and pH are the most strongly correlated parameters with bacterial abundance in the thermophilic and cooling phases/mature compost respectively. Differential abundance analysis revealed 810 ESVs annotated as species significantly varied in relative abundance between Litter and Young phase, 653 between the Young and Middle phases, 1182 between Middle and Aged phases and 663 between Aged phase and mature Compost. These changes indicated that structural carbohydrates and lignin degrading species were abundant at the beginning of the thermophilic phase, especially members of the Firmicute and Actinobacteria phyla. A high diversity of species capable of putative ammonification and denitrification were consistently found throughout the composting phases, whereas a limited number of nitrifying bacteria were identified and were significantly enriched within the later mesophilic composting phases. High microbial community resolution also revealed unexpected species which could be beneficial for agricultural soils enriched with mature compost or for the deployment of environmental and plant biotechnologies. Understanding the dynamics of these microbial communities could lead to improved waste management strategies and the development of input-specific composting protocols to optimize carbon and nitrogen transformation and promote a diverse and functional microflora in mature compost.

Expanding the genomic encyclopedia of Actinobacteria with 824 isolate reference genomes

The phylum Actinobacteria includes important human pathogens like Mycobacterium tuberculosis and Corynebacterium diphtheriae and renowned producers of secondary metabolites of commercial interest, yet only a small part of its diversity is represented by sequenced genomes. Here, we present 824 actinobacterial isolate genomes in the context of a phylum-wide analysis of 6,700 genomes including public isolates and metagenome-assembled genomes (MAGs). We estimate that only 30%-50% of projected actinobacterial phylogenetic diversity possesses genomic representation via isolates and MAGs. A comparison of gene functions reveals novel determinants of host-microbe interaction as well as environment-specific adaptations such as potential antimicrobial peptides. We identify plasmids and prophages across isolates and uncover extensive prophage diversity structured mainly by host taxonomy. Analysis of >80,000 biosynthetic gene clusters reveals that horizontal gene transfer and gene loss shape secondary metabolite repertoire across taxa. Our observations illustrate the essential role of and need for high-quality isolate genome sequences.

Genome-Based Taxonomic Classification of the Phylum Actinobacteria

The application of phylogenetic taxonomic procedures led to improvements in the classification of bacteria assigned to the phylum Actinobacteria but even so there remains a need to further clarify relationships within a taxon that encompasses organisms of agricultural, biotechnological, clinical, and ecological importance. Classification of the morphologically diverse bacteria belonging to this large phylum based on a limited number of features has proved to be difficult, not least when taxonomic decisions rested heavily on interpretation of poorly resolved 16S rRNA gene trees. Here, draft genome sequences of a large collection of actinobacterial type strains were used to infer phylogenetic trees from genome-scale data using principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families, and genera, as well as many species and a few subspecies were shown to be in need of revision leading to proposals for the recognition of 2 orders, 10 families, and 17 genera, as well as the transfer of over 100 species to other genera. In addition, emended descriptions are given for many species mainly involving the addition of data on genome size and DNA G+C content, the former can be considered to be a valuable taxonomic marker in actinobacterial systematics. Many of the incongruities detected when the results of the present study were compared with existing classifications had been recognized from 16S rRNA gene trees though whole-genome phylogenies proved to be much better resolved. The few significant incongruities found between 16S/23S rRNA and whole genome trees underline the pitfalls inherent in phylogenies based upon single gene sequences. Similarly good congruence was found between the discontinuous distribution of phenotypic properties and taxa delineated in the phylogenetic trees though diverse non-monophyletic taxa appeared to be based on the use of plesiomorphic character states as diagnostic features.

Isolation of Uncultured Bacteria from Antarctica Using Long Incubation Periods and Low Nutritional Media

Uncultured microorganisms comprise most of the microbial diversity existing on our planet. Despite advances in environmental sequencing and single-cell genomics, in-depth studies about bacterial metabolism and screening of novel bioproducts can only be assessed by culturing microbes in the laboratory. Here we report uncultured, or recalcitrant, microorganisms from an Antarctic soil sample, using relatively simple methods: oligotrophic media, extended incubation periods, observation under stereo microscopy, and selection of slow-growing bacteria. We managed to isolate several rare microorganisms belonging to infrequently isolated or recently described genera, for example Lapillicoccus, Flavitalea, Quadrisphaera, Motilibacter, and Polymorphobacter. Additionally, we obtained isolates presenting 16S rRNA sequence similarity ranging from 92.08 to 94.46% with any other known cultured species, including two distinct isolates from the class Thermoleophilia, that although common in Antarctic soils (as identified by metagenomics), was never reported to be isolated from such samples. Our data indicates that simple methods are still useful for cultivating recalcitrant microorganisms, even when dealing with samples from extreme environments.

Korean indigenous bacterial species with valid names belonging to the phylum Actinobacteria

To understand the isolation and classification state of actinobacterial species with valid names for Korean indigenous isolates, isolation source, regional origin, and taxonomic affiliation of the isolates were studied. At the time of this writing, the phylum Actinobacteria consisted of only one class, Actinobacteria, including five subclasses, 10 orders, 56 families, and 330 genera. Moreover, new taxa of this phylum continue to be discovered. Korean actinobacterial species with a valid name has been reported from 1995 as Tsukamurella inchonensis isolated from a clinical specimen. In 1997, Streptomyces seoulensis was validated with the isolate from the natural Korean environment. Until Feb. 2016, 256 actinobacterial species with valid names originated from Korean territory were listed on LPSN. The species were affiliated with three subclasses (Acidimicrobidae, Actinobacteridae, and Rubrobacteridae), four orders (Acidimicrobiales, Actinomycetales, Bifidobacteriales, and Solirubrobacterales), 12 suborders, 36 families, and 93 genera. Most of the species belonged to the subclass Actinobacteridae, and almost of the members of this subclass were affiliated with the order Actinomycetales. A number of novel isolates belonged to the families Nocardioidaceae, Microbacteriaceae, Intrasporangiaceae, and Streptomycetaceae as well as the genera Nocardioides, Streptomyces, and Microbacterium. Twenty-six novel genera and one novel family, Motilibacteraceae, were created first with Korean indigenous isolates. Most of the Korean indigenous actionobacterial species were isolated from natural environments such as soil, seawater, tidal flat sediment, and fresh-water. A considerable number of species were isolated from artificial resources such as fermented foods, wastewater, compost, biofilm, and water-cooling systems or clinical specimens. Korean indigenous actinobacterial species were isolated from whole territory of Korea, and especially a large number of species were from Jeju, Gyeonggi, Jeonnam, Daejeon, and Chungnam. A large number of novel actinobacterial species continue to be discovered since the Korean government is encouraging the search for new bacterial species and researchers are endeavoring to find out novel strains from extreme or untapped environments.

Monashia flava gen. nov., sp. nov., an actinobacterium of the family Intrasporangiaceae

A novel actinobacterial strain, MUSC 78^T, was isolated from a mangrove soil collected from Peninsular Malaysia. The taxonomic status of this strain was determined using a polyphasic approach. Comparative 16S rRNA gene sequence analysis revealed that strain MUSC 78^T represented a novel lineage within the class Actinobacteria. Strain MUSC 78^T formed a distinct clade in the family Intrasporangiaceae and was related most closely to members of the genera Terrabacter (98.3-96.8 % 16S rRNA gene sequence similarity), Intrasporangium (98.2-96.8 %), Humibacillus (97.2 %), Janibacter (97.0-95.3 %), Terracoccus (96.8 %), Kribbia (96.6 %), Phycicoccus (96.2-94.7 %), Knoellia (96.1-94.8 %), Tetrasphaera (96.0-94.9 %) and Lapillicoccus (95.9 %). Cells were irregular rod-shaped or cocci and stained Gram-positive. The cell-wall peptidoglycan type was A3γ, with ll-diaminopimelic acid as the diagnostic diamino acid. The main cell-wall sugar was mannose and lower amounts of galactose and rhamnose were present. The predominant menaquinone was MK-8(H₄). The polar lipid profile consisted of phosphatidylglycerol, phosphatidylinositol, phosphatidylethanolamine, diphosphatidylglycerol and phosphoglycolipid. The predominant fatty acids were iso-C_15 : 0, anteiso-C_15 : 0 and iso-C_16 : 0. The DNA G+C content was 73.1 mol%. Based on this polyphasic study, MUSC 78^T exhibited phylogenetic and phenotypic differences from members of the genera of the family Intrasporangiaceae, and therefore a novel species of a new genus, Monashia flava gen. nov., sp. nov., is proposed. The type strain of Monashia flava is MUSC 78^T ( = DSM 29621^T = MCCC 1K00454^T = NBRC 110749^T).

Oryzobacter terrae gen. nov., sp. nov., isolated from paddy soil

A bacterial strain, PSGM2-16(T), was isolated from a pot of paddy soil grown with rice in Suwon region, Republic of Korea, and was characterized as having aerobic, Gram-stain-positive, short-rod-shaped cells with one polar flagellum. The 16S rRNA gene sequence of strain PSGM2-16(T) revealed the highest sequence similarities with Knoellia locipacati DMZ1T (97.4%), Fodinibacter luteus YIM C003(T) (97.2%) and Lapillicoccus jejuensis R-Ac013(T) (97.0%), and the phylogenetic tree showed that strain PSGM2-16(T) formed a subgroup with Ornithinibacter aureus HB09001(T) and F. luteus YIM C003(T) within the family Intrasporangiaceae. The major fatty acids (>10% of the total fatty acids) of strain PSGM2-16(T) were iso-C16 : 0, C17 : 1ω8c and iso-C14 : 0. The predominant menaquinone was MK-8(H4). The polar lipids present were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, three aminophospholipids and two phospholipids. The peptidoglycan was type A4γ with meso-diaminopimelic acid as the diagnostic diamino acid. DNA-DNA hybridization values between strain PSGM2-16(T) and closely related taxa were much less than 70%. The genomic DNA G+C content of strain PSGM2-16(T) was 70.0 mol%. On the basis of the evidence presented, it is concluded that strain PSGM2-16(T) represents a novel species of a new genus in the family Intrasporangiaceae, for which the name Oryzobacter terrae gen. nov., sp. nov. is proposed. The type strain of the type species is PSGM2-16(T) ( = KACC 17299(T)= DSM 27137(T)= NBRC 109598(T)).

Kineococcus rhizosphaerae sp. nov., isolated from rhizosphere soil

An orange-coloured actinomycete, designated strain RP-B16T, was isolated from a rhizosphere soil. Cells of strain RP-B16T were strictly aerobic, Gram-positive-staining, oxidase-negative, catalase-positive, motile cocci. A phylogenetic tree, based on 16S rRNA gene sequences, showed that members of the genus Kineococcus were divided into two independent clusters and that strain RP-B16T formed a coherent clade with the type strains of Kineococcus aurantiacus (99.5% sequence similarity) and Kineococcus radiotolerans (99.1%). Levels of 16S rRNA gene sequence similarity between strain RP-B16T and Kineococcus marinus KST3-3T and 'Kineococcus tegulae' T2A-S27 were lower than 97.0%. Chemotaxonomic characteristics were typical of the genus Kineococcus in having meso-diaminopimelic acid as the diagnostic diamino acid, MK-9(H2) as the predominant menaquinone, a polar lipid profile comprising diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol and two unknown phospholipids, anteiso-C15:0 as the predominant fatty acid and a DNA G+C content of 73.8 mol%. Strain RP-B16T showed levels of DNA-DNA relatedness of 34.6-37.3% to Kineococcus aurantiacus DSM 7487T and 31.2-32.7% to Kineococcus radiotolerans DSM 14245T. On the basis of phenotypic features and DNA-DNA hybridization data, strain RP-B16T is considered to represent a novel species of the genus Kineococcus, for which the name Kineococcus rhizosphaerae sp. nov. is proposed. The type strain is RP-B16T (=KCTC 19366T=DSM 19711T).

Fodinibacter luteus gen. nov., sp. nov., an actinobacterium isolated from a salt mine

A Gram-positive-staining, aerobic, catalase- and oxidase-positive, irregular short rod-shaped actinobacterium, designated strain YIM C003T, was isolated from a salt mine in Yunnan, PR China. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain YIM C003T was most closely related to strains of the genera Knoellia (94.2-96.0% similarity), Oryzihumus (95.6%), Terrabacter (94.9-95.4%), Janibacter (94.9-95.4%), Kribbia (95.0%), Lapillicoccus (95.0%) and Phycicoccus (94.2-95.0%) of the family Intrasporangiaceae and that it formed an independent monophyletic lineage with three strains of Oryzihumus leptocrescens. The DNA G+C content of strain YIM C003T was 72.0 mol%. The diagnostic cell-wall diamino acid was meso-diaminopimelic acid. The predominant menaquinone was MK-8(H4). Mycolic acids were not detected. The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol and two unknown phospholipids. The major cellular fatty acids were C18:1omega9c and C16:0. These chemotaxonomic properties, together with data from phylogenetic analysis, enabled the novel isolate to be differentiated from all other members of the family. A novel species in a new genus, Fodinibacter luteus gen. nov., sp. nov., is proposed, with strain YIM C003T (=DSM 21208T=CCTCC AA 208036T) as the type strain of Fodinibacter luteus.

An update of the structure and 16S rRNA gene sequence-based definition of higher ranks of the class Actinobacteria, with the proposal of two new suborders and four new families and emended descriptions of the existing higher taxa

The higher ranks of the class Actinobacteria were proposed and described in 1997. At each rank, the taxa were delineated from each other solely on the basis of 16S rRNA gene sequence phylogenetic clustering and taxon-specific 16S rRNA signature nucleotides. In the past 10 years, many novel members have been assigned to this class while, at the same time, some members have been reclassified. The new 16S rRNA gene sequence information and the changes in phylogenetic positions of some taxa influence decisions about which 16S rRNA nucleotides to define as taxon-specific. As a consequence, the phylogenetic relationships of Actinobacteria at higher levels may need to be reconstructed. Here, we present new 16S rRNA signature nucleotide patterns of taxa above the family level and indicate the affiliation of genera to families. These sets replace the signatures published in 1997. In addition, Actinopolysporineae subord. nov. and Actinopolysporaceae fam. nov. are proposed to accommodate the genus Actinopolyspora, Kineosporiineae subord. nov. and Kineosporiaceae fam. nov. are proposed to accommodate the genera Kineococcus, Kineosporia and Quadrisphaera, Beutenbergiaceae fam. nov. is proposed to accommodate the genera Beutenbergia, Georgenia and Salana and Cryptosporangiaceae fam. nov. is proposed to accommodate the genus Cryptosporangium. The families Nocardiaceae and Gordoniaceae are proposed to be combined in an emended family Nocardiaceae. Emended descriptions are also proposed for most of the other higher taxa.