Microbial Diversity of Psychrotolerant Bacteria Isolated from Wild Flora of Andes Mountains and Patagonia of Chile towards the Selection of Plant Growth-Promoting Bacterial Consortia to Alleviate Cold Stress in Plants

Cold stress decreases the growth and productivity of agricultural crops. Psychrotolerant plant growth-promoting bacteria (PGPB) may protect and promote plant growth at low temperatures. The aims of this study were to isolate and characterize psychrotolerant PGPB from wild flora of Andes Mountains and Patagonia of Chile and to formulate PGPB consortia. Psychrotolerant strains were isolated from 11 wild plants (rhizosphere and phyllosphere) during winter of 2015. For the first time, bacteria associated with Calycera, Orites, and Chusquea plant genera were reported. More than 50% of the 130 isolates showed ≥33% bacterial cell survival at temperatures below zero. Seventy strains of Pseudomonas, Curtobacterium, Janthinobacterium, Stenotrophomonas, Serratia, Brevundimonas, Xanthomonas, Frondihabitans, Arthrobacter, Pseudarthrobacter, Paenarthrobacter, Brachybacterium, Clavibacter, Sporosarcina, Bacillus, Solibacillus, Flavobacterium, and Pedobacter genera were identified by 16S rRNA gene sequence analyses. Ten strains were selected based on psychrotolerance, auxin production, phosphate solubilization, presence of nifH (nitrogenase reductase) and acdS (1-aminocyclopropane-1-carboxylate (ACC) deaminase) genes, and anti-phytopathogenic activities. Two of the three bacterial consortia formulated promoted tomato plant growth under normal and cold stress conditions. The bacterial consortium composed of Pseudomonas sp. TmR5a & Curtobacterium sp. BmP22c that possesses ACC deaminase and ice recrystallization inhibition activities is a promising candidate for future cold stress studies.

Lacisediminihabitans profunda gen. nov., sp. nov., a member of the family Microbacteriaceae isolated from freshwater sediment

A novel Gram-stain-positive bacterial strain, CHu50b-6-2^T, was isolated from a 67-cm-long sediment core collected from the Daechung Reservoir at a water depth of 17 m, Daejeon, Republic of Korea. The cells of strain CHu50b-6-2^T were aerobic non-motile and formed yellow colonies on R2A agar. The phylogenetic analysis based on 16S rRNA gene sequencing indicated that the strain formed a separate lineage within the family Microbacteriaceae, exhibiting 98.0%, 97.7% and 97.6% 16S rRNA gene sequence similarities to Glaciihabitans tibetensis KCTC 29148^T, Frigoribacterium faeni KACC 20509^T and Lysinibacter cavernae DSM 27960^T, respectively. The phylogenetic trees revealed that strain CHu50b-6-2^T did not show a clear affiliation to any genus within the family Microbacteriaceae. The chemotaxonomic results showed B1α type peptidoglacan containg 2, 4-diaminobutyric acid (DAB) as the diagnostic diamino acid, MK-10 as the predominant respiratory menaquinone, diphosphatidylglycerol, phosphatidylglycerol, and an unidentified glycolipid as the major polar lipids, anteiso-C_15:0, iso-C_16:0, and anteiso-C_17:0 as the major fatty acids, and a DNA G + C content of 67.3 mol%. The combined genotypic and phenotypic data showed that strain CHu50b-6-2^T could be distinguished from all genera within the family Microbacteriaceae and represents a novel genus, Lacisediminihabitans gen. nov., with the name Lacisediminihabitans profunda sp. nov., in the family Microbacteriaceae. The type strain is CHu50b-6-2^T (= KCTC 49081^T = JCM 32673^T).

Planctomonas deserti gen. nov., sp. nov., a new member of the family Microbacteriaceae isolated from soil of the Taklamakan desert

A Gram-staining-positive, aerobic, irregular coccoid- to ovoid-shaped, non-spore-forming and motile bacterium, designated strain 13S1-3^T, was isolated from a soil sample from the rhizosphere of Tamarix collected in the Taklamakan desert in Xinjiang Uygur Autonomous Region, PR China. The strain was examined by a polyphasic approach to clarify its taxonomic position. Strain 13S1-3^T grew optimally at 28-30 °C, pH 7.0 and with 0-1 % (w/v) NaCl. The cell-wall peptidoglycan was of the B2γ type and contained d-alanine, d-glutamic acid, glycine, d-2,4-diaminobutyric acid and l-2,4-diaminobutyric acid. Ribose, xylose, glucose and galactose were detected as cell-wall sugars. The acyl type of the muramic acid was acetyl. The predominant menaquinones were MK-12, MK-11, MK-13 and MK-10. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, two unidentified glycolipids and one unidentified phospholipid. The major whole-cell fatty acids were anteiso-C15 : 0, anteiso-C17 : 0 and iso-C16 : 0. The DNA G+C content was 70.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that 13S1-3^T represented a member of the family Microbacteriaceae and showed the highest level of 16S rRNA gene sequence similarity with Frondihabitans australicus E1HC-02^T (97.11 %). Phylogenetic trees revealed that 13S1-3^T formed a distinct lineage with respect to closely related genera within the family Microbacteriaceae. On the basis of the results of phylogenetic, phenotypic and chemotaxonomic analyses, 13S1-3^T is distinguishable from phylogenetically related genera in the family Microbacteriaceae, and represents a novel species of a new genus, for which the name Planctomonas deserti gen. nov., sp. nov. is proposed. The type strain is 13S1-3^T (=KCTC 49115^T=CGMCC 1.16554^T).

Subtercola lobariae sp. nov., an actinobacterium of the family Microbacteriaceae isolated from the lichen Lobaria retigera

An actinobacterium, designated strain 9583bT, was isolated from the lichen Lobaria retigera collected from Jiaozi Snow Mountain, Yunnan Province, China. Cells of strain 9583bT were Gram-stain-positive, aerobic, catalase-positive and oxidase-negative. The strain have a short rod-shaped, irregular morphology, and could grow at the temperature range of 4 to 28 °C. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 9583bT belonged to the genus Subtercola in the family Microbacteriaceae, and shared highest sequence similarity with the type strains of Subtercola frigoramans and Subtercola boreus (96.8 and 95.6 %, respectively). The peptidoglycan type was B2γ, with diaminobutyric acid as the diagnostic diamino acid. The polar lipids comprised of phosphatidylglycerol, diphosphatidylglycerol, five unidentified glycolipids and three unidentified phospholipids. The respiratory quinone was determined to be MK-10. While the major fatty acids (>5 %) of strain 9583bT were anteiso-C15 : 0, C14 : 0 2-OH and iso-C16 : 0, the 1,1-dimethoxy-alkanes included a-15 : 0 DMA, i-16 : 0 DMA, a-17 : 0 DMA and i-15 : 0 DMA. The genomic DNA G+C content of strain 9583bT was 66.8 mol%. On the basis of the phylogenetic, phenotypic and chemotaxonomic data in this study, strain 9583bT represents a novel species of the genus Subtercola, for which the name Subtercola lobariae sp. nov. is proposed. The type strain is 9583bT (=CGMCC 1.12976T=DSM 103962T).

Lysinibacter cavernae gen. nov., sp. nov., a new member of the family Microbacteriaceae isolated from a karst cave

A Gram-stain-positive, aerobic, straight or slightly bent rod-shaped, non-motile, non-spore-forming bacterium, designated strain CC5-806T, was isolated from a soil sample collected from a wild karst cave in the Wulong region, Chongqing, PR China and examined using a polyphasic approach to clarify its taxonomic position. This bacterium did not produce substrate mycelium or aerial hyphae, and no diffusible pigments were observed on the media tested. Strain CC5-806T grew optimally without NaCl at 20 °C and at pH 7.0. Phylogenetic analysis, based on 16S rRNA gene sequences, indicated that strain CC5-806T belonged to the family Microbacteriaceae and showed the highest levels of 16S rRNA gene sequence similarities with Frigoribacterium endophyticum EGI 6500707T (97.56 %), Frigoribacterium faeni 801T (97.53 %) and Glaciihabitans tibetensis MP203T (97.42 %). Phylogenetic trees revealed that strain CC5-806T did not show a clear affiliation to any genus within the family Microbacteriaceae. The DNA G+C content of strain CC5-806T was 62.6 mol%. The cell-wall peptidoglycan contained l-lysine as a diagnostic diamino acid. The predominant menaquinones were MK-11, MK-10 and MK-9. Phosphatidylglycerol, diphosphatidylglycerol, an unidentified glycolipid, four unidentified phospholipids and other polar lipids were detected in the polar lipid extracts. The major fatty acids were anteiso-C15 : 0, iso-C16 : 0 and iso-C14 : 0. On the basis of the phylogenetic analysis, and phenotypic and chemotaxonomic characteristics, strain CC5-806T was distinguishable from phylogenetically related genera in the family Microbacteriaceae. It represents a novel species of a novel genus, for which the name Lysinibacter cavernae gen. nov., sp. nov. is proposed. The type strain is CC5-806T ( = DSM 27960T = CGMCC 1.14983T).

Complete genome sequence of Frondihabitans sp. strain PAMC28766, a novel carotenoid-producing and radiation-resistant strain isolated from an Antarctic lichen

Here, we report the first complete genome sequence of Frondihabitans sp. strain PAMC28766, which was found to consist of three plasmids, one chromosome (4,345,897bp), and a series of genes involved in carotenoid biosynthesis and nucleotide excision repair. An analysis of the Frondihabitans sp. PAMC28766 genome will improve our understanding of the carotenoid biosynthesis pathway. Furthermore, the sequence data will provide novel insight into UV radiation-resistance in extremely cold environments.

Deciphering microbial landscapes of fish eggs to mitigate emerging diseases

Animals and plants are increasingly suffering from diseases caused by fungi and oomycetes. These emerging pathogens are now recognized as a global threat to biodiversity and food security. Among oomycetes, Saprolegnia species cause significant declines in fish and amphibian populations. Fish eggs have an immature adaptive immune system and depend on nonspecific innate defences to ward off pathogens. Here, meta-taxonomic analyses revealed that Atlantic salmon eggs are home to diverse fungal, oomycete and bacterial communities. Although virulent Saprolegnia isolates were found in all salmon egg samples, a low incidence of Saprolegniosis was strongly correlated with a high richness and abundance of specific commensal Actinobacteria, with the genus Frondihabitans (Microbacteriaceae) effectively inhibiting attachment of Saprolegniato salmon eggs. These results highlight that fundamental insights into microbial landscapes of fish eggs may provide new sustainable means to mitigate emerging diseases.

Glaciihabitans tibetensis gen. nov., sp. nov., a psychrotolerant bacterium of the family Microbacteriaceae, isolated from glacier ice water

A Gram-stain-positive, aerobic, non-spore-forming, short-rod-shaped bacterium, designated strain MP203T, was isolated from ice water of Midui Glacier in Tibet Autonomous Region, China. The strain was psychrotolerant, growing at 0–25 °C. 16S rRNA gene sequence analysis showed that strain MP203T was most similar to Frigoribacterium faeni NBRC 103066T, Compostimonas suwonensis KACC 13354T, Frigoribacterium mesophilum KCTC 19311T, Marisediminicola antarctica CCTCC AB 209077T and Alpinimonas psychrophila JCM 18951T, with similarities of 97.4, 97.2, 97.2, 97.1 and 97.1 %, respectively. The maximum-likelihood phylogenetic tree indicated that strain MP203T clustered with nine genera of the family Microbacteriaceae , namely Frigoribacterium , Compostimonas , Marisediminicola , Alpinimonas , Frondihabitans , Clavibacter , Subtercola , Klugiella and Agreia . However, bootstrap analysis showed that there was no significance in the branching pattern of the linage comprising strain MP203T and any existing generic lineage of the family Microbacteriaceae . DNA–DNA hybridization results indicated levels of relatedness between strain MP203T and Marisediminicola antarctica CCTCC AB 209077T, Frigoribacterium faeni NBRC 103066T, Frigoribacterium mesophilum KCTC 19311T, Compostimonas suwonensis KACC 13354T and Alpinimonas psychrophila JCM 18951T were 25.8±7.3, 29.6±7.6, 19.7±6.7, 16.0±4.2 and 12.4±5.1 % (mean±sd), respectively. The G+C content of the genomic DNA was 64.1 mol%. Analysis of the cell-wall peptidoglycan revealed that the peptidoglycan structure of strain MP203T was B10 type with Gly[l-Hse]–d-Glu–d-DAB, containing 2, 4-diaminobutyric acid (DAB) as a diagnostic amino acid. The cell-wall sugars were rhamnose, ribose, mannose and glucose. The major fatty acids were anteiso-C15 : 0, iso-C16 : 0 and anteiso A-C15 : 1. An unusual compound identified as anteiso-C15 : 0-DMA (1, 1-dimethoxy-anteiso-pentadecane) was also present in strain MP203T. The predominant menaquinone was MK-10. Diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), one unknown glycolipid and four unknown lipids were detected in the polar lipid extracts. As strain MP203T was distinguishable from phylogenetically related genera in the family Microbacteriaceae in terms of its physiological and chemotaxonomic characteristics and phylogenetic position, it was considered to represent a novel species of a new genus. Thus, the name Glaciihabitans tibetensis gen. nov., sp. nov. is proposed. The type strain of Glaciihabitans tibetensis is MP203T ( = CGMCC 1.12484T = KCTC 29148T).

The correct name of the taxon that contains the type strain of Rhodococcus equi

Based on a nomenclatural point of view, the name Rhodococcus equi is associated, as required by the Bacteriological Code, with a defined position, rank and circumscription. A search of the literature indicates that the name Rhodococcus equi (Magnusson 1923) Goodfellow and Alderson 1977 has also been shown to be a synonym of Corynebacterium equi Magnusson 1923, Corynebacterium hoagii (Morse 1912) Eberson 1918 and Nocardia restricta (Turfitt 1944) McClung 1974. Application of the rules of the Bacteriological Code together with the currently inferred taxonomic concept associated with the species bearing the name Rhodococcus equi indicates that this is not the correct name of this taxon and the use of that name in the context of a circumscription that includes the type strain of the species Corynebacterium hoagii is contrary to the Rules of the Code.

Description of Galbitalea soli gen. nov., sp. nov., and Frondihabitans sucicola sp. nov

Bacterial strains KIS82-1(T) and GRS42(T) were isolated from soil and from sap of Acer mono, respectively, in the Republic of Korea. Both strains were aerobic, Gram-stain-positive, mesophilic, rod-shaped and motile. Phylogenetically, both strains belonged to the family Microbacteriaceae of the phylum Actinobacteria. The 16S rRNA gene sequence of strain KIS82-1(T) showed the highest similarity to those of Frondihabitans peucedani RS-15(T) (97.6%), Frigoribacterium mesophilum MSL-08(T) (97.2%) and Labedella gwakjiensis KSW2-17(T) (97.0%), while strain GRS42(T) showed the highest 16S rRNA gene sequence similarity to Frondihabitans peucedani RS-15(T) (98.7%), Frondihabitans cladoniiphilus CafT13(T) (98.4%), Frondihabitans australicus E1HC-02(T) (98.2%) and Frigoribacterium faeni 801(T) (97.3%). The 16S rRNA gene sequence similarity between GRS42(T) and KIS82-1(T) was 97.0%. Phylogenetic trees indicated that strain GRS42(T) was firmly grouped into the genus Frondihabitans, while strain KIS82-1(T) did not show a clear affiliation to any genus within the family Microbacteriaceae. Strain KIS82-1(T) showed type B1β peptidoglycan with 2,4-diamino-L-butyric acid as the diamino acid. It had MK-11, MK-10 and MK-12 as respiratory quinones, anteiso-C(15 : 0), iso-C(16: 0) and iso-C(14 : 0) as major cellular fatty acids and diphosphatidylglycerol, phosphatidylglycerol and an unknown glycolipid as predominant polar lipids. The peptidoglycan of strain GRS42(T) was of type B2β with D-ornithine as the diamino acid. The strain contained MK-8, MK-9 and MK-7 as respiratory quinones, summed feature 8 (C(18 : 1)ω6c and/or C(18 : 1)ω7c) as major cellular fatty acid and diphosphatidylglycerol, phosphatidylglycerol and three unknown glycolipids as predominant polar lipids. Strain GRS42(T) revealed low DNA-DNA hybridization (<50% relatedness) with closely related strains. Based on the data obtained in the present polyphasic taxonomic study, we propose that strain KIS82-1(T) represents a novel genus and species and that strain GRS42(T) represents a novel species in the family Microbacteriaceae. The genus Galbitalea gen. nov. is proposed, with strain KIS82-1(T) ( = KACC 15520(T) = NBRC 108727(T)) as the type strain of the type species, Galbitalea soli sp. nov. Strain GRS42(T) ( = KACC 15521(T) = NBRC 108728(T)) is proposed as the type strain of Frondihabitans sucicola sp. nov.

Compostimonas suwonensis gen. nov., sp. nov., isolated from spent mushroom compost

A Gram-positive, aerobic, non-motile, short rod, designated SMC46T, was isolated from a spent mushroom compost sample collected in the Suwon region, South Korea. 16S rRNA gene sequence analysis revealed that strain SMC46T was a member of the family Microbacteriaceae ; however, the isolate formed a branch separate from other genera within the family. Sequence similarity between strain SMC46T and other members of the family Microbacteriaceae was ≤97 %, the highest sequence similarity being with Frigoribacterium faeni 801T and Frondihabitans australicus E1HC-02T (both 97.0 %). Some chemotaxonomic properties of strain SMC46T were consistent with those of the family Microbacteriaceae : MK-11 and MK-12 as the predominant menaquinones, anteiso-C15 : 0, iso-C16 : 0 and anteiso-C17 : 0 as the major cellular fatty acids and diphosphatidylglycerol, phosphatidylglycerol and an unidentified glycolipid as the polar lipids. However, strain SMC46T contained a B-type peptidoglycan not previously found in the family Microbacteriaceae . The DNA G+C content was 68 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic distinctiveness, strain SMC46T was considered to represent a novel genus and species in the family Microbacteriaceae , for which the name Compostimonas suwonensis gen. nov., sp. nov. is proposed. The type strain of the type species is SMC46T ( = KACC 13354T  = NBRC 106304T).

Alpinimonas psychrophila gen. nov., sp. nov., an actinobacterium of the family Microbacteriaceae isolated from alpine glacier cryoconite

A Gram-type positive, Gram-reaction variable, non-motile, psychrophilic actinobacterium, designated Cr8-25(T), was isolated from alpine glacier cryoconite and was able to grow well over a temperature range of 1-15 °C. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain Cr8-25(T) belonged to the family Microbacteriaceae and showed highest 16S rRNA gene sequence similarity with Klugiella xanthotipulae 44C3(T) (97.0%). However, strain Cr8-25(T) could be differentiated from the type strain of K. xanthotipulae on the level of genomospecies by a DNA-DNA relatedness value of only 37.2%. Strain Cr8-25(T) contained a cell-wall peptidoglycan that was cross-linked according to the B-type, which is based on 2,4-diaminobutyric acid. The cell wall contained the sugars galactose, fucose and rhamnose. The predominant cellular fatty acids of strain Cr8-25(T) were C(15:0) anteiso (64.6%) and iso-C(16:0) (22.5%) and the major menaquinones were MK-11 and MK-10. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and unknown glycolipids. The G+C content of the genomic DNA was 58.8 mol%. On the basis of the phenotypic characteristics, phylogenetic and chemotaxonomic analyses and DNA-DNA relatedness data, strain Cr8-25(T) represents a novel species of a new genus in the family Microbacteriaceae, for which the name Alpinimonas psychrophila gen. nov., sp. nov. is proposed. The type strain is Cr8-25(T) (=DSM 23737(T)=LMG 26215(T)).

Frondihabitans cladoniiphilus sp. nov., an actinobacterium of the family Microbacteriaceae isolated from lichen, and emended description of the genus Frondihabitans

A novel actinobacterium, designated strain CafT13(T), was isolated from the thallus of the reindeer lichen Cladonia arbuscula sampled in the Austrian Alps (Koralpe). The organism was aerobic, with rod- to irregular-shaped cells (often forming dense clusters of cells when grown in liquid medium), Gram-stain-positive, oxidase-negative, catalase-positive and non-motile. It was able to grow at 1 °C and at low to neutral pH, but not above 30 °C or at high pH. The peptidoglycan type was B2β with ornithine as the diagnostic diamino acid. The menaquinones were MK-7 and MK-8. The polar lipid profile comprised diphosphatidylglycerol, phosphatidylglycerol, three unidentified phospholipids, three unidentified glycolipids and one unidentified aminolipid. The predominant fatty acids were C(18:1), C(14:0) 2-OH, C(17:1)ω9c, C(16:0) and anteiso-C(15:0). The mean DNA G+C content of strain CafT13(T) was 69.0±0.17 mol%. 16S rRNA gene sequence analysis showed that strain CafT13(T) belongs to the family Microbacteriaceae, within the genus Frondihabitans. The mean level of DNA-DNA relatedness between strain CafT13(T) and the type strain of Frondihabitans australicus was 35.2±5.23%. The enzyme spectrum of strain CafT13(T) differentiated it from recognized species of the genus Frondihabitans. Based on molecular, chemotaxonomic and physiological data, strain CafT13(T) is considered to represent a novel species of the genus Frondihabitans, for which the name Frondihabitans cladoniiphilus sp. nov. is proposed; the type strain is CafT13(T) (=DSM 23273(T)=LMG 25550(T)).

Frondihabitans peucedani sp. nov., an actinobacterium isolated from rhizosphere soil, and emended description of the genus Frondihabitans Greene et al. 2009

A novel actinobacterium, designated RS-15T, was isolated from rhizosphere soil of a plant (Peucedanum japonicum Thunb.) on Mara Island, Jeju, Republic of Korea. Cells were strictly aerobic, Gram-stain-positive, oxidase-negative, catalase-positive, non-motile, irregular, short rods. The peptidoglycan in the cell wall was of the B2beta type with ornithine as the diagnostic diamino acid. The major menaquinone was MK-8; small amounts of MK-9 and MK-7 were also present. The polar lipids contained phosphatidylglycerol, five unknown glycolipids, three unknown phospholipids and two unknown lipids. Mycolic acids were not present. The predominant fatty acids were summed feature 7 (one or more of C18:1omega9c, C18:1omega12t and C18:1omega7c), anteiso-C15:0 and C14:0 2-OH. The DNA G+C content was 68.3 mol%. 16S rRNA gene sequence analysis showed that strain RS-15T belonged to the family Microbacteriaceae and formed a tight phylogenetic cluster with Frondihabitans australicus E1HC-02T (98.5% sequence similarity). The DNA-DNA relatedness between strain RS-15T and Frondihabitans australicus DSM 17894T was 17.2% (17.1%, duplicate measurements). On the basis of the physiological, chemotaxonomic and DNA-DNA hybridization data, strain RS-15T is considered to represent a novel species of the genus Frondihabitans, for which the name Frondihabitans peucedani sp. nov. is proposed. The type strain is RS-15T (=KCTC 13435T =DSM 22180T). An emended description of the genus Frondihabitans is also presented.

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.