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The Genus Kurthia: Cell Wall Composition and DNA Base Content
System. Appl. Microbial. 5, 220-224 (1984)
Department of Microbiology, University of Reading, London Road, Reading RGI SAQ,
U.K.
The Genus Kurthia: Cell Wall Composition and DNA Base Content STEVEN SHAWl and RONALD M. KEDDIE
Received November 2, 1983
Summary The G + C contents of the DNA's of 21 Kurthia zopfii and 13 K. gibsonii strains were found to fall in the range 36.6-37.8 mol% G + C. The distinctive cell wall amino acids of these strains were lysine and aspartic acid. The DNA base ratios and cell wall compositions of a number of other Kurthia-like strains were also determined. Key words: Kurthia - Kurthia zopfii - Kurthia gibsonii - DNA - Cell Wall- Taxonomy
Introduction A numerical taxonomic study of new isolates and named strains of the genus Kurthia (Shaw and Keddie, 1983 a) revealed two major clusters considered to represent the species K. zopfii and K. gibsonii. Further studies (Shaw and Keddie, 1983 b) revealed differences in vitamin nutrition between the two species. The purpose of the present work was to determine the cell wall compositions and DNA base ratios of the 21 K. zopfii and 13 K. gibsonii strains previously studied in order to test the homogeneity of the two species and to see if further differences between the two would be revealed. Eleven strains which conformed with the definition of Kurthia in Bergey's Manual (Keddie and Rogosa, 1974) but which did not group with either of the two Kurthia species were also examined together with a few Bacillus strains and a strain of a Gram-positive non-spore-forming rod isolated from Panda faeces (Kobatake et al., 1977). The 49 strains studied are listed in Table 1; full details are described elsewhere (Shaw and Keddie, 1983a).
1
Present address: Watney Mann and Truman Brewers Ltd, London SW14 8JD, England.
Chemotaxonomy of Kurthia
221
Materials and Methods Strains were grown in YNB (Shaw and Keddie, 1983 a) at 25°C on an orbital shaker until late log phase. After checking purity, the cells were harvested by centrifugation, washed twice and stored at - 18 °C until required. The DNA was isolated and purified by the methods described by Garvie (1976) and stored in standard saline citrate (SSC), at 4 °C with a few drops of chloroform. The % G + C content was determined in SSC by the thermal denaturation (Tm) method (Marmur and Doty, 1962). The Tm values were determined twice and if the two values agreed within 0.1 °C, the average was used to calculate the G + C content. The equation used to calculate mol% G + C values was derived from that of De Ley (1970) but is expressed relative to the Tm of reference DNA from Escherichia coli K-12 (NCTC 10538) as recommended by Mandel et al. (1970). The Tm of this strain was found to be 91.5 °C and its G + C content was taken as 51 % (De Ley, 1970; Mandel et aI., 1970). Thus the equation used was mol% G + C = 51 + 2.44 (Tm - 91.5). Cell walls were prepared by the alkali method described by Keddie and Cure (1977) and as a check cell wall preparations from a number of strains were also obtained by the method described by Cummins and Johnson (1971). The chromatographic techniques were similar to those used by Keddie and Cure (1977).
Results and Discussion The G + C contents of most strains studied fell in the range 35-45% G + C (Table 1). The G + C contents of K. zopfii NCTC 404 (38.15%, Belikova et aI., 1980) and strain K59 (65.7%, Kobatake et aI., 1977) have been published previously. The values in the present work were 37.1 % and 67.3% respectively. The G + C content of the type strain of K. zopfii (NCIB 9878) was 37.6%, that of the type strain of K. gibsonii (NCIB 9758) was 36.8%. The cell wall diamino acid of all Kurthia and Kurthia-like strains was lysine, while that from strain K59 was ornithine (Table 1). Most strains also contained aspartic acid. These results are in accord with the cell wall composition reported for K. zopfii NCTC 404 by Belikova et a1. (1980) and with the peptidoglycan structure of K. zopfii NCTC 404 and 405 reported by Schleifer and Kandler (1972). However, Kobatake et al. (1977) reported that the cell wall diamino acid of strain K59, isolated from Panda faeces, was lysine whereas repeated analyses in the present study showed that the diamino acid was in fact ornithine. Sugars were rarely detected in the walls of Kurthia strains and thus were of no taxonomic value in this study. Therefore they have not been included in Table 1. All strains of K. gibsonii and K. zopfii examined were homogeneous with respect to their cell wall composition. They contained lysine and aspartic acid as the distinctive amino acids. In addition their G + C contents were in the remarkably narrow range of 36.6-37.8%. The range of 1.2% G + C is well within that considered to be acceptable at generic level (De Ley, 1969). The range for each of the two species was 1.1 % G + C thus supporting their specific status. That the two species were indistinguishable on the basis of G + C content and cell wall composition as determined by simple qualitative analysis does not contradict their position as separate species. More complex cell wall analyses may have revealed differences between the two species but since Schleifer and Kandler (1972) studied only K.zopfii strains (NCTC 404, 405) it is not possible to say what differences if any, occur in the peptidoglycan structures of the two species.
222
S. Shaw and R. M. Keddie
Table1. DNA base contents and cell walla compositions of Kurthiazopfii,K.gibsonii and other strains Species or Group
Strain number
Average Tm °C
mol% G+C
K. gibsonii
K3 (NCIB 9758)*, K12, K50, K68 K8, K9, K29 (NCIB 10495), K31 (NCIB 10499), K69, K75 Kl (NCIB 9756), K2 (NCIB 9757), K57 (NCIB 8603)
83.65-85.7 85.8 -85.85
36.7-36.8 37.1-37.2
86.05-86.1
37.7-37.8
K7, K17, K35, K39, K40, K66, K80 K4 (NCTC 404), Kll, K13, K14, K36, K54, K76, K78, K84 K5 (NCIB 9878)", K33, K34, K37, K58 (NCTC 405)
85.6 -85.7 85.8 -85.9
36.6-36.8 37.1-37.3
86.0 -86.05
37.6-37.7
K. zopfii
Kurthia-like strains
K22 (NCMB 1054) K24 K28 K45 K47 K48 K49 K60 K63 K70 K81
99.5 88.05 85.5 86.9 87.3 86.35 88.6 85.9 87.3 85.95 85.15
70.6 42.6 36.4 39.8 40.8 38.4 43.9 37.3 40.8 37.5 35.5
Bacillus strains
K83 KI05 (NCIB 9370)* Bac. K123 (NCTC 7585) sphaericus
85.2 85.9 88.85
35.6 37.3 44.5
Other strains
K59
98.2
67.3
& All K. zopfii, K. gibsonii and most other strains contained lysine and aspartic acid in the cell wall; strain K59 contained ornithine and aspartic acid, and strains K49, K70 and K81 contained lysine but not aspartic acid. Tm °C thermal denaturation temperature ,. type strain (see Shaw and Keddie, 1983 a) NCTC National Collection of Type Cultures, London NCIB National Collection of Industrial Bacteria, Aberdeen NCMB National Collection of Marine Bacteria, Aberdeen.
Of the eleven Kurthia-like strains which were separated from the main Kurthia area in the numerical study of Shaw and Keddie (1983 a) only one strain (K22) with a G + C content of 70.6% could be clearly distinguished from the genus as represented by K. zopfii and K. gibsonii. All other strains have G + C contents close to the range described for the two species and all had lysine as cell wall diamino acid and most contained aspartic acid (Table 1). However, although the taxonomic position of these strains remains unresolved, two interesting features emerged. Three strains isolated from Antarctic peat (K45, K47, K48) which grouped together in the numerical study (Shaw and Keddie, 1983 a) had G + C contents in the narrow
Chemotaxonomy of Kurthia
223
range 38.4-40.8% and contained lysine and aspartic acid as distinctive cell wall components. Also an asporogenous strain (K60), which was associated with two Bacillus strains (K83, K105) in the numerical study and showed a relatively close phenetic similarity to the two Kurthia species, had a G + C content of 37.3% and lysine and aspartic acid in the cell wall. These features seem to suggest that strain K60 has affinities with both the Kurthia spp. and the Bacillus spp. mentioned. The chemotaxonomic data presented here support the conclusions of the numerical phenetic study of Shaw and Keddie (1983 a) that there is little relationship between Kurthia and the coryneform and nocardioform bacteria. Also most Bacillus spp. contain meso-diaminopimelic acid in the cell wall peptidoglycan (Schleifer and Kandler, 1972) and were well separated from the two Kurthia species in the study of Shaw and Keddie (1983a). However, exceptions were the type strain of B.sphaericus (NClB 9370) and an obligately aerobic Bacillus isolate (K83) which had quite a high phenetic similarity to the two Kurthia spp. Their DNA base ratios, 37.3% (NCIB 9370) and 35.6% (K83), and their principal cell wall amino acids, lysine and aspartic acid, are in accord with this association. Also the peptidoglycan structure of B. sphaericus is reported to be similar to that of K. zopfii (Schleifer and Kandler, 1972) and the major isoprenoid quinones of NClB 9370 are, like those of Kurthia, unsaturated menaquinones with seven isoprene units (MK-7; Collins and Jones, 1979). However, a second B. sphaericus strain (NCTC 7585) grouped less closely with Kurthia than NCIB 9370 in the numerical study and although the wall preparation of this strain contained lysine and aspartic acid, its G + C content, 44.5%, was about 7.0% higher than those of the Kurthia strains. However, 165 rRNA cataloguing studies (Ludwig et aI., 1981) have shown that K. zopfii ATCC 6900 (= NCTC 405) is only distantly related to Bacillus spp. (including B. sphaericus, E.Stackebrandt, pers. comm.). The fermentative genera Listeria and Brochothrix resemble Kurthia in some chemotaxonomic characters (see Goodfellow et aI., 1980; Shaw and Keddie, 1983 a) but their cell wall diamino acid is meso-diaminopimelic acid (Schleifer and Kandler, 1972) and they differ in polar lipid composition from Kurthia (Goodfellow et aI., 1980). Acknowledgement. RMK gratefully acknowledges receipt of Agricultural Research Council Grant AC 45196 for the provision of equipment.
References Belikova, V. I., Cherevach, N. V., Baryshnikova, I. M., Kalakutskii, I. V.: Morphologic, physiologic and biochemical characteristics of Kurthia zopfii. Microbiology 49, 51-55 (1980) Collins, M. D., Jones, D.: Isoprenoid quinone composition as a guide to the classification of Sporolactobacillus and possibly related bacteria. J. appl. Bact. 47, 293-297 (1979) Cummins, C.S., Johnson, J.I.: Taxonomy of the clostridia: wall composition and DNA homologies in Clostridium butyricum and other butyric acid producing clostridia. J. gen. Microbiol. 67, 33-46 (1971) De Ley, J.: Molecular data in microbial systematics. In: Systematic Biology. Nat. Acad. Sci. Bull. 1962, 248-279 (1969) De Ley, j.: Re-examination of the association between melting point, buoyant density and chemical base composition of deoxyribonucleic acid. J. Bact. 101, 738-754 (1970) 15 Systematic and Applied Microbiology, Vol. 5
224
S. Shaw and R. M. Keddie
Garvie, E.I.: Hybridisation between the deoxyribonucleic acids of some strains of heterofermentative lactic acid bacteria. Int. J. system. Bact. 26, 116-122 (1976) Goodfellow, M., Collins, M.D., Minnikin, D.E.: Fatty acid and polar lipid composition in the classification of Kurthia. J. appl. Bact. 48, 269-276 (1980) Keddie, R. M., Cure, G. L.: The cell wall composition and distribution of free mycolic acids in named strains of coryneform bacteria and in isolates from various natural sources. J. appl. Bact. 42, 229-252 (1977) Keddie, R.M., Rogosa, M.: Genus Kurthia. In: Bergey's manual of determinative bacteriology (R. E. Buchanan, N. E. Gibbons, eds.), 8th ed. Baltimore, Willams and Wilkins 1974 Kobatake, M., Kurata, H., Komagata, K.: A radioresistant Gram positive asporogenous rod isolated from the faeces of a Giant Panda (Ailuropoda melanoleuca). J. gen. MicrobioI. 100, 43-48 (1977) Ludwig, W., Seewaldt, E., Schleifer, K. H., Stackebrandt, E.: The phylogenetic status of Kurthia zopfii. FEMS Microbiol. Lett. 10, 193-197 (1981) Mandel, M., Igambi, L., Bergendahl, J., Dodson, M. L., Scheltgen, E.: Correlation of melting temperature and cesium chloride buoyant density of bacterial deoxyribonucleic acid. J. Bact. 101, 333-338 (1970) Marmur, ]., Doty, P.: Determination of the base composition of deoxyribonucleic acid from its thermal denaturation temperature. J. molec. BioI. 5, 109-118 (1962) Schleifer, K. H., Kandler, 0.: Peptidoglycan types of bacterial cell walls and their taxonomic implications. Bact. Rev. 36, 407-477 (1972) Shaw, S., Keddie, R. M.: A numerical taxonomic study of the genus Kurthia with a revised description of K. zopfii and a description of K. gibsonii sp. nov. System. Appl. MicrobioI. 4, 253-276 (1983 a) Shaw, S., Keddie, R. M.: The vitamin requirements of Kurthia zopfii and Kurthia gibsonii. System. Appl. Microbiol. 4,439-443 (1983 b).
Dr. R. M. Keddie, Department of Microbiology, University of Reading, London Road, Reading, RG15AQ, England
Department of Microbiology, University of Reading, London Road, Reading RGI SAQ,
U.K.
The Genus Kurthia: Cell Wall Composition and DNA Base Content STEVEN SHAWl and RONALD M. KEDDIE
Received November 2, 1983
Summary The G + C contents of the DNA's of 21 Kurthia zopfii and 13 K. gibsonii strains were found to fall in the range 36.6-37.8 mol% G + C. The distinctive cell wall amino acids of these strains were lysine and aspartic acid. The DNA base ratios and cell wall compositions of a number of other Kurthia-like strains were also determined. Key words: Kurthia - Kurthia zopfii - Kurthia gibsonii - DNA - Cell Wall- Taxonomy
Introduction A numerical taxonomic study of new isolates and named strains of the genus Kurthia (Shaw and Keddie, 1983 a) revealed two major clusters considered to represent the species K. zopfii and K. gibsonii. Further studies (Shaw and Keddie, 1983 b) revealed differences in vitamin nutrition between the two species. The purpose of the present work was to determine the cell wall compositions and DNA base ratios of the 21 K. zopfii and 13 K. gibsonii strains previously studied in order to test the homogeneity of the two species and to see if further differences between the two would be revealed. Eleven strains which conformed with the definition of Kurthia in Bergey's Manual (Keddie and Rogosa, 1974) but which did not group with either of the two Kurthia species were also examined together with a few Bacillus strains and a strain of a Gram-positive non-spore-forming rod isolated from Panda faeces (Kobatake et al., 1977). The 49 strains studied are listed in Table 1; full details are described elsewhere (Shaw and Keddie, 1983a).
1
Present address: Watney Mann and Truman Brewers Ltd, London SW14 8JD, England.
Chemotaxonomy of Kurthia
221
Materials and Methods Strains were grown in YNB (Shaw and Keddie, 1983 a) at 25°C on an orbital shaker until late log phase. After checking purity, the cells were harvested by centrifugation, washed twice and stored at - 18 °C until required. The DNA was isolated and purified by the methods described by Garvie (1976) and stored in standard saline citrate (SSC), at 4 °C with a few drops of chloroform. The % G + C content was determined in SSC by the thermal denaturation (Tm) method (Marmur and Doty, 1962). The Tm values were determined twice and if the two values agreed within 0.1 °C, the average was used to calculate the G + C content. The equation used to calculate mol% G + C values was derived from that of De Ley (1970) but is expressed relative to the Tm of reference DNA from Escherichia coli K-12 (NCTC 10538) as recommended by Mandel et al. (1970). The Tm of this strain was found to be 91.5 °C and its G + C content was taken as 51 % (De Ley, 1970; Mandel et aI., 1970). Thus the equation used was mol% G + C = 51 + 2.44 (Tm - 91.5). Cell walls were prepared by the alkali method described by Keddie and Cure (1977) and as a check cell wall preparations from a number of strains were also obtained by the method described by Cummins and Johnson (1971). The chromatographic techniques were similar to those used by Keddie and Cure (1977).
Results and Discussion The G + C contents of most strains studied fell in the range 35-45% G + C (Table 1). The G + C contents of K. zopfii NCTC 404 (38.15%, Belikova et aI., 1980) and strain K59 (65.7%, Kobatake et aI., 1977) have been published previously. The values in the present work were 37.1 % and 67.3% respectively. The G + C content of the type strain of K. zopfii (NCIB 9878) was 37.6%, that of the type strain of K. gibsonii (NCIB 9758) was 36.8%. The cell wall diamino acid of all Kurthia and Kurthia-like strains was lysine, while that from strain K59 was ornithine (Table 1). Most strains also contained aspartic acid. These results are in accord with the cell wall composition reported for K. zopfii NCTC 404 by Belikova et a1. (1980) and with the peptidoglycan structure of K. zopfii NCTC 404 and 405 reported by Schleifer and Kandler (1972). However, Kobatake et al. (1977) reported that the cell wall diamino acid of strain K59, isolated from Panda faeces, was lysine whereas repeated analyses in the present study showed that the diamino acid was in fact ornithine. Sugars were rarely detected in the walls of Kurthia strains and thus were of no taxonomic value in this study. Therefore they have not been included in Table 1. All strains of K. gibsonii and K. zopfii examined were homogeneous with respect to their cell wall composition. They contained lysine and aspartic acid as the distinctive amino acids. In addition their G + C contents were in the remarkably narrow range of 36.6-37.8%. The range of 1.2% G + C is well within that considered to be acceptable at generic level (De Ley, 1969). The range for each of the two species was 1.1 % G + C thus supporting their specific status. That the two species were indistinguishable on the basis of G + C content and cell wall composition as determined by simple qualitative analysis does not contradict their position as separate species. More complex cell wall analyses may have revealed differences between the two species but since Schleifer and Kandler (1972) studied only K.zopfii strains (NCTC 404, 405) it is not possible to say what differences if any, occur in the peptidoglycan structures of the two species.
222
S. Shaw and R. M. Keddie
Table1. DNA base contents and cell walla compositions of Kurthiazopfii,K.gibsonii and other strains Species or Group
Strain number
Average Tm °C
mol% G+C
K. gibsonii
K3 (NCIB 9758)*, K12, K50, K68 K8, K9, K29 (NCIB 10495), K31 (NCIB 10499), K69, K75 Kl (NCIB 9756), K2 (NCIB 9757), K57 (NCIB 8603)
83.65-85.7 85.8 -85.85
36.7-36.8 37.1-37.2
86.05-86.1
37.7-37.8
K7, K17, K35, K39, K40, K66, K80 K4 (NCTC 404), Kll, K13, K14, K36, K54, K76, K78, K84 K5 (NCIB 9878)", K33, K34, K37, K58 (NCTC 405)
85.6 -85.7 85.8 -85.9
36.6-36.8 37.1-37.3
86.0 -86.05
37.6-37.7
K. zopfii
Kurthia-like strains
K22 (NCMB 1054) K24 K28 K45 K47 K48 K49 K60 K63 K70 K81
99.5 88.05 85.5 86.9 87.3 86.35 88.6 85.9 87.3 85.95 85.15
70.6 42.6 36.4 39.8 40.8 38.4 43.9 37.3 40.8 37.5 35.5
Bacillus strains
K83 KI05 (NCIB 9370)* Bac. K123 (NCTC 7585) sphaericus
85.2 85.9 88.85
35.6 37.3 44.5
Other strains
K59
98.2
67.3
& All K. zopfii, K. gibsonii and most other strains contained lysine and aspartic acid in the cell wall; strain K59 contained ornithine and aspartic acid, and strains K49, K70 and K81 contained lysine but not aspartic acid. Tm °C thermal denaturation temperature ,. type strain (see Shaw and Keddie, 1983 a) NCTC National Collection of Type Cultures, London NCIB National Collection of Industrial Bacteria, Aberdeen NCMB National Collection of Marine Bacteria, Aberdeen.
Of the eleven Kurthia-like strains which were separated from the main Kurthia area in the numerical study of Shaw and Keddie (1983 a) only one strain (K22) with a G + C content of 70.6% could be clearly distinguished from the genus as represented by K. zopfii and K. gibsonii. All other strains have G + C contents close to the range described for the two species and all had lysine as cell wall diamino acid and most contained aspartic acid (Table 1). However, although the taxonomic position of these strains remains unresolved, two interesting features emerged. Three strains isolated from Antarctic peat (K45, K47, K48) which grouped together in the numerical study (Shaw and Keddie, 1983 a) had G + C contents in the narrow
Chemotaxonomy of Kurthia
223
range 38.4-40.8% and contained lysine and aspartic acid as distinctive cell wall components. Also an asporogenous strain (K60), which was associated with two Bacillus strains (K83, K105) in the numerical study and showed a relatively close phenetic similarity to the two Kurthia species, had a G + C content of 37.3% and lysine and aspartic acid in the cell wall. These features seem to suggest that strain K60 has affinities with both the Kurthia spp. and the Bacillus spp. mentioned. The chemotaxonomic data presented here support the conclusions of the numerical phenetic study of Shaw and Keddie (1983 a) that there is little relationship between Kurthia and the coryneform and nocardioform bacteria. Also most Bacillus spp. contain meso-diaminopimelic acid in the cell wall peptidoglycan (Schleifer and Kandler, 1972) and were well separated from the two Kurthia species in the study of Shaw and Keddie (1983a). However, exceptions were the type strain of B.sphaericus (NClB 9370) and an obligately aerobic Bacillus isolate (K83) which had quite a high phenetic similarity to the two Kurthia spp. Their DNA base ratios, 37.3% (NCIB 9370) and 35.6% (K83), and their principal cell wall amino acids, lysine and aspartic acid, are in accord with this association. Also the peptidoglycan structure of B. sphaericus is reported to be similar to that of K. zopfii (Schleifer and Kandler, 1972) and the major isoprenoid quinones of NClB 9370 are, like those of Kurthia, unsaturated menaquinones with seven isoprene units (MK-7; Collins and Jones, 1979). However, a second B. sphaericus strain (NCTC 7585) grouped less closely with Kurthia than NCIB 9370 in the numerical study and although the wall preparation of this strain contained lysine and aspartic acid, its G + C content, 44.5%, was about 7.0% higher than those of the Kurthia strains. However, 165 rRNA cataloguing studies (Ludwig et aI., 1981) have shown that K. zopfii ATCC 6900 (= NCTC 405) is only distantly related to Bacillus spp. (including B. sphaericus, E.Stackebrandt, pers. comm.). The fermentative genera Listeria and Brochothrix resemble Kurthia in some chemotaxonomic characters (see Goodfellow et aI., 1980; Shaw and Keddie, 1983 a) but their cell wall diamino acid is meso-diaminopimelic acid (Schleifer and Kandler, 1972) and they differ in polar lipid composition from Kurthia (Goodfellow et aI., 1980). Acknowledgement. RMK gratefully acknowledges receipt of Agricultural Research Council Grant AC 45196 for the provision of equipment.
References Belikova, V. I., Cherevach, N. V., Baryshnikova, I. M., Kalakutskii, I. V.: Morphologic, physiologic and biochemical characteristics of Kurthia zopfii. Microbiology 49, 51-55 (1980) Collins, M. D., Jones, D.: Isoprenoid quinone composition as a guide to the classification of Sporolactobacillus and possibly related bacteria. J. appl. Bact. 47, 293-297 (1979) Cummins, C.S., Johnson, J.I.: Taxonomy of the clostridia: wall composition and DNA homologies in Clostridium butyricum and other butyric acid producing clostridia. J. gen. Microbiol. 67, 33-46 (1971) De Ley, J.: Molecular data in microbial systematics. In: Systematic Biology. Nat. Acad. Sci. Bull. 1962, 248-279 (1969) De Ley, j.: Re-examination of the association between melting point, buoyant density and chemical base composition of deoxyribonucleic acid. J. Bact. 101, 738-754 (1970) 15 Systematic and Applied Microbiology, Vol. 5
224
S. Shaw and R. M. Keddie
Garvie, E.I.: Hybridisation between the deoxyribonucleic acids of some strains of heterofermentative lactic acid bacteria. Int. J. system. Bact. 26, 116-122 (1976) Goodfellow, M., Collins, M.D., Minnikin, D.E.: Fatty acid and polar lipid composition in the classification of Kurthia. J. appl. Bact. 48, 269-276 (1980) Keddie, R. M., Cure, G. L.: The cell wall composition and distribution of free mycolic acids in named strains of coryneform bacteria and in isolates from various natural sources. J. appl. Bact. 42, 229-252 (1977) Keddie, R.M., Rogosa, M.: Genus Kurthia. In: Bergey's manual of determinative bacteriology (R. E. Buchanan, N. E. Gibbons, eds.), 8th ed. Baltimore, Willams and Wilkins 1974 Kobatake, M., Kurata, H., Komagata, K.: A radioresistant Gram positive asporogenous rod isolated from the faeces of a Giant Panda (Ailuropoda melanoleuca). J. gen. MicrobioI. 100, 43-48 (1977) Ludwig, W., Seewaldt, E., Schleifer, K. H., Stackebrandt, E.: The phylogenetic status of Kurthia zopfii. FEMS Microbiol. Lett. 10, 193-197 (1981) Mandel, M., Igambi, L., Bergendahl, J., Dodson, M. L., Scheltgen, E.: Correlation of melting temperature and cesium chloride buoyant density of bacterial deoxyribonucleic acid. J. Bact. 101, 333-338 (1970) Marmur, ]., Doty, P.: Determination of the base composition of deoxyribonucleic acid from its thermal denaturation temperature. J. molec. BioI. 5, 109-118 (1962) Schleifer, K. H., Kandler, 0.: Peptidoglycan types of bacterial cell walls and their taxonomic implications. Bact. Rev. 36, 407-477 (1972) Shaw, S., Keddie, R. M.: A numerical taxonomic study of the genus Kurthia with a revised description of K. zopfii and a description of K. gibsonii sp. nov. System. Appl. MicrobioI. 4, 253-276 (1983 a) Shaw, S., Keddie, R. M.: The vitamin requirements of Kurthia zopfii and Kurthia gibsonii. System. Appl. Microbiol. 4,439-443 (1983 b).
Dr. R. M. Keddie, Department of Microbiology, University of Reading, London Road, Reading, RG15AQ, England