Actinomycetes University of Udine, Mycology Department ISSN: 0732-0574 Vol. 6, Num. 1, 1995

A New Genus of Actinomycetales : Cathayosporangium alboflavum gen. nov., sp. nov.

H. Runmao, L. Junying and Y. Guozhu

Sichuan Industrial Institute of Antibiotics, Sichuan, Chengdu, P.R. of China 610051

Code Number: AC95004
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Abstract.

A new aerobic mesophilic genus of Actinomycetales, Cathayosporangium, is described. The microorganism produces a filamentous growth which is differentiated into a vegetative mycelium and an aerial mycelium. Cathayosporangium strains are characterised by the formation of globose sporangia at the end of sporangiophores of various lengths borne on aerial hyphae, with each sporangium containing a single zoospore. Cell wall contains meso-diaminopimelic acid, asparagine and glutamine. Madurose, galactose, glucose and ribose are the sugars detected in whole cell hydrolysates. The type species of the new genus is Cathayosporangium alboflavum (type strain NA 945112 = ATCC 51497).

In the course of a study of actinomycete populations in soils collected in the eastern part of China, 20 uncommon strains were isolated in 1993 in areas of the Anhui and Jiangsu provinces. The organisms are characterised by small globose sporangia containing single zoospores. Their chemotaxonomical characters include a cell wall composition consisting of meso-diaminopimelic acid and asparagine, glutamine and madurose, galactose, glucose and ribose as whole cell sugars.

Morphological characteristics preclude the placement of the organisms in any of the previously described genera. A new genus, Cathayosporangium, is proposed for the isolates. Strain NA 945112 is designated as the type strain of the type species, Cathayosporangium alboflavum.

Materials and Methods

Strains. Strains NA 945112T (T = type strain), 944457, 945059, 945061, 945062, 945099, 945101, 945103, 945104, 945106, 945110, 945116, 945121, 945122, 945124, 945128, 945130, 945132, 945233 and 946543 were isolated from soils collected in areas of the Anhui and Jiangsu provinces. All strains were isolated by a new capillary technique (Runmao et al., 1994). Stock cultures were grown on plates at 28øC using International Streptomyces Project (ISP) media 2 to 7 (Shirling and Gottlieb, 1966) and HV agar (Hayakawa and Nonomura, 1987).

Morphological characterisation. The morphology of sporangia and spores was examined by scanning (SEM) and transmission (TEM) electron microscopy on cultures grown on HV agar. For SEM agar blocks were cut from cultures grown at 28øC on ISP medium 3. Blocks were trimmed, dehydrated through a graded ethanol series, transferred to isoamyl acetate and then critical point dried using liquid carbon dioxide. Specimens were sputter coated with gold-palladium. Sporangial features were observed by TEM using whole-mount preparations. To examine motile spores, agar block containing sporangia were placed in a tube filled with 0.5ml of sterile tap water and kept for 30-50min at room temperature. One drop of the spore suspension was placed on Formvar coated 300-mesh copper grids, stained with 0.125% phosphotungstic acid, air dried and examined by TEM.

Physiological characterisation. Tests for the utilisation of different carbon sources were carried out on ISP medium 9 (Shirling and Gottlieb, 1966).

Chemotaxonomic characterisation. Chemical composition of cell walls was determined according to Becker et al. (1965).

Whole cells analysis was carried out according to Lechevalier (1968).

Figure 1. Micromorphology of C.alboflavum, strain NA945112T. Aerial hyphae bearing single sporangia (A and B)., sporangiospores (zoospores) with a subpolar flagella (C and D) and ultrathin of mature sporangia (E). Magnification: B 14,000x, C and D 19,000, E 36,000. In A bar equals 5um.

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       Medium   Vegetative mycelium   Aerial mycelium     Sporangium
       ISP      Amount and colour     Amount and colour   formation 
       
       2       Good, wrinkled         Good, whitish yellow   Good
       3       Good, hyaline          Good, whitish yellow   Good
       4       Good, ivory            Good, whitish yellow   Good
       5       Moderate, hyaline      Good, white            Good
       6       Moderate, hyaline      Absent                 None
       7       Moderate, light brown  Poor, white            Good
       
       

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Results and Discussion

Description of Cathayosporangium gen.nov. Cathayosporangium (Ca.tha.yo. spo.ran'gi.um. M.L.adj. Cathayan, Chinese; Gr.n. spora, a seed; Gr.n. angeion, a vessel; M.L.neut.n. Cathayosporangium, Chinese sporangium).

Aerobic, gram positive and non acid fast.

Well developed, non fragmenting, irregularly branched vegetative hyphae (0.15-0.3um in diameter), penetrating the agar and forming on its surface compact, raised, tough colonies. Aerial hyphae (0.2-0.4um in diameter) bear small, globose sporangia (1.4 to 1.8um in diameter) (Fig.1, A, B) containing single (Fig. 1, E), zoospores, oval in shape (1.0- 1.8 x 0.7-0.8um) (Fig.1, C, D). In water sporangia release zoospores with a single subpolar flagellum (Fig.1, C, D).

The peptidoglycan of the cell wall contains meso- diaminopimelic acid, asparagine and glutamine. Madurose, galactose, glucose and ribose are the sugars detected in whole cell hydrolysates.

Mesophilic.

Good growth at temperatures between 28ø and 37øC and at pH 6.0-8.0. The type species of the genus is Cathayosporangium alboflavum sp.nov.

Description of Cathayosporangium alboflavum sp.nov. Cathayosporangium alboflavum (al.bo.fla'vum. M.L.neut. adj. alboflavum, whitish yellow).

Morphological characteristics as for the genus. Cultural characteristics of the type strain are shown in Table 1. Neither soluble nor melanin like pigments are produced. Utilises maltose, galactose, inulin, D-mannitol, lactose and trehalose. No growth on D-glucose, sucrose, D-xylose, D- ribose, salicin, L-sorbose, galactitol, D-glucitol, L- rhamnose, melezitose, L-arabinose, L-arabitol and melibiose. Milk is slowly peptonised and coagulated, starch is not hydrolysed, gelatine is liquefied (Table 2).

The type strain of the species is NA 945112 deposited in the American Type Culture Collection under accession number ATCC 51497.

Recognised genera of the actinomycetes forming sporangial structures include (Goodfellow, 1989; Petrolini et al., 1993; Runmao et al., 1993) Actinoplanes, Ampullariella, Dactylosporangium, Kibdelosporangium, Pilimelia, Planobispora, Planomonospora, Planopolyspora, Planotetraspora, Spirillospora, Streptoalloteichus and Streptosporangium. Members of these genera, however, have morphological and chemotaxonomic features that differ from those of our isolates.

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                                        STRAIN NA
       
       Carbon      945112    944457  945059 945061  945099  945106
       Source      945124
       Utilisation 945643
       
       L-Arabinose   -          -       +      -       +      -
       Glucose       -          -       -      -       -      +
       L-Rhamnose    -          -       -      -       +      -
       Trehalose     +          +       +      -       +      +
       Lactose       +          +       -      +       +      -
       D-Ribose      -          -       -      -       -      +
       Salicin       -          +       -      -       -      -
       Melezitose    -          +       -      -       -      +          

Table 2. Physiological and biochemical characteristics of strains of C.alboflavum. All strains peptonise milk, hydrolyse casein, gelatine and starch and utilise galactose, inulin, maltose and mannitol. No strain utilises L-arabitol, D-glucitol, melibiose, L-sorbose, sucrose, D-xylose as sole carbon source.

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Morphology and cell wall chemistry of Cathayosporangium alboflavum are similar to those of the genera Streptosporangium, Spirillospora and Planomonospora. The genus Streptosporangium, as currently described, produces globose sporangia on the aerial mycelium and non motile sporangiospores. The genus Spirillospora has sporangia containing numerous zoospores. Planomonospora forms sporangia with single zoospores, but arranged in characteristic palm leaf patterns.

Generic classification of sporangia forming actinomycetes is currently based on morphology of the sporangia, number of spores and their arrangement within the sporangium. On the basis of these characteristics it is not possible to place the new isolates in any of the above mentioned genera. Thus, the new genus, Cathayosporangium gen.nov. and the type species Cathayosporangium alboflavum sp.nov., are proposed.

Acknowledgements.

We thank Dr. Chen-Weiqun and Dr.Zeng-Jiayu of the Central Analysis Dept., Sichuan University for transmission and scanning electron microscopy.

References

Becker, B., M.P.Lechevalier & H.A.Lechevalier (1965). Chemical composition of cell-wall preparations from strains of various form genera of aerobic actinomycetes. Appl.Microbiol., 13: 236-243

Goodfellow, M. (1989). Maduromycetes. In: S.T.Williams, E.Sharpe & J.G.Holt (eds.) Bergey's Manual of Systematic Bacteriology. Williams & Wilkins, Baltimore, Vol.4, pp. 2509-2551

Hayakawa, M. & H.Nonomura (1987). Humic acid-vitamin agar, a new medium for the selective isolation of soil actinomycetes. J.Ferment.Technol., 65: 501- 509

Lechevalier, M.P. (1968). Identification of aerobic actinomycetes of clinical importance. J.Lab. Clin.Med., 71: 934-944

Petrolini, B., S.Quaroni, M.Saracchi & P. Sardi (1993). A new genus of the maduromycetes: Planopolyspora gen.nov. Actinomycetes, 4: 8-16

Runmao, H., M.Lianjun & W.Guizhen (1994). Distribution of soil actinomycetes in North-East China. Actinomycetes, 5: 12-13

Runmao, H., W.Guizhen & L.Jungying (1993). A new genus of actinomycetes, Planotetraspora gen.nov. Int.J.Syst.Bacteriol., 43: 468-470

Shirling, E.B. & D.Gottlieb (1966). Methods for characterization of Streptomyces species. Int.J. Syst.Bacteriol., 16: 313-340.

Copyright 1995 CECT

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