The Utilization of L-Sorbose by Some Pathogenic Species Of

THE UTILIZATION OF L.SORBOSE BY SOME PATHOGENIC SPECIES OF PHYLLOSTICTA

By K. S. BmG~I (Botany Department, University of Ailahabad. lndia) Received November 26, 1962

(Communicated by Dr, R. N. Tandon, •.^ so.)

L-So~3osE, a ketohexose, has been reported to be unutilizable for many fungi and even toxic for several others. The toxicity is evidenced by the death of the hyphal tips followed by meagre branching of the mycelium below the killed portions (Tatum et aL, 1949; Lilly and Barnett, 1953). It has been suggested in the literature that probably this sugar interferes with the respiratory pathway and the growth of those micro-organisms which are exclusively dependent on this pathway is restricted or sometimes even inhibited completely. The importance of L-sorbose, in the metabolism of fungi, volunteered the need for the present studies.

MATERIALS AND METHODS

Twelve species of Phyllosticta, which were conunon leaf-spot pathogens of the ornamental plants and fruit trees in Northern India, were selected for the present investigations. A nutrient solution containing 10g. glucose, 3"5g. KNO~, 1-75g. KH~POa, 0-75g. MgSO4. 7H~O, 100/~g. thiamine, 10/~g. biotin and 2 ml. of trace element solution dissolved in one litre of twice distilled water served as the basal medium. Glucose of the basal medium was individually replaced by maltose, sucrose and sorbose in order to examine the sole effect of the above sugars. In another series of experiment, sorbose was used in combination with either of the above three sugars (glucose, maltose or sucrose). In each case the quantity of sugars was so adjusted, so as to furnish 4,000 rag. of carbon per litre. 25 ml. of autoclaved solutions dispensed in 150 ml. Erlenmeyer flasks served as nutrient. Tripli- cate sets were used for each series. Agar discs of 4 mm. diameter from 10 days old colonies of each isolate were used as inocula. Three incubation periods at the intervals of five days were used after which the colonies were washed, filtered and dried on Whatman filter paper No. 42. The dry weights of the colonies have been employed for assessing the growth. 230 Utilization of L-Sovbose by Some Pathogenic" Species of Phy!losticta 231

Some flasks from each series were separated for the chromatographic analysis of the medium from which 0-005 c.c. of solution was aseptically taken out with a sterilized micropipette and was placed in the chromatograms. The daily analysis of the culture medium was accomplished in this way. The details of the chromatographic technique were similar to those adopted by Tandon and Bilgrami (1958).

EXPERIMENTAL

Table I manifests that only seven species were able to accomplish slight growth on L-sorbose while five of them, viz., P. buteae, P. dracaenae, p. dardanoi, P. morifolia and P. glaucispora completely failed to respond on this sugar as the sole source of carbon. Table I also depicts that other three sugars, viz., maltose, sucrose and glucose were individually very good sources. The incubation time of those species of Phyllosticta, which did not show any response on sorbose within 15 days, was raised to 60 days but the inoculum did not exhibit any sign of growth even after such a prolonged incubation. Chromatographic analysis of the media containing individual sugars indicated that the band of sorbose remained undiminished till the end of the incubation time while the other three sugars were consumed by the 10th day. Microscopic examination of the coloniesshowed thekiUing of the hyphal tips of all the isolates on the sorbose medium. Table I clearly shows that the dry weight yield of all the species was quite satisfactory on combina- tions of sorbose with other three sugars. Chromatographic analysis of such media showed a distinct decrease in the intensity of the sorbose band.

DISCUSSION

Oddoux (1952), Benedict et aL (1955), Leaphart (1956) and Pisano and Plucker (1958) reported that a number of fungi were capable of using this ketohexose well. The present species of Phyllosticta, however, differed from the fungi listed by the above workers in not showing a favourable response towards L-sorbose, when this sugar was used as a sole carbon source, but its behaviour markedly improved in a dual carbon source with glucose, maltose or sucrose as its complementary associates. Lilly and Barnett (1953) reported that inhibitory effect of sorbose was more pronounced in presence of maltose rather than glucose or sucrose. The present results did not manifest any such variations. This experiment was elaborated further where the normal supply of maltose was maintained in the medium and 5 g./litr© of extra sorbose was added to that solution. Regular chromatographic 232 K.S. BILGRAMI

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°~ Utilization of L-Sorbose by Some Pathogenic Species of PhyUosticta 233 analysis of such medium revealed that only one oligosaccharide had developed in the medium and that too had a very faint band. Such results suggest that possibly in the presence Of sorbose, these fungi utilize the glucose fraction more quickly due to which very little quantity is left to participate in the synthesis of an oligosaccharide. It is also speculated that growth for few days is only at the expense of maltose (hydrolysed to glucose) and sorbose starts its contribution only slowly and gradually after some growth has been achieved within the first few days. Had sorbose participated from the begin- ning, probably there would not have been so much demand for all the available glucose in the medium.

SUMMARY The utilization of L-sorbose by twelve pathogenic species of Phyllosticta was investigated. Seven species attained meagre growth on this substance when it was used as sole carbon source in the medium while the other five species, viz., P. buteae, P. dracaenae, P. dardanoi, P. morifolia and P. glaucispora completely failed to accomplish any growth even if the incubation period was raised to sixty days. Chromatographic analysis of the medium revealed that utilizability of sorbose was considerably increased if it was used in combination with good sources like sucrose, maltose or glucose, etc.

ACKNOWLEDGEMENT The author is grateful to Professor R. N. Tandon, Head of the Botany Department, Allahabad University, for his encouragement and critically examining this manuscript.

REFERENCES

1. Benedict, R. G., Ptidharn, App. Microbiol., 1955, 3, 1-6. T. O., Lindenfeler, L. A. and Jackson, R.W. 2, Leaphart, C. D. "'Physiological studies of some fungi associated wilh pole- blight of western white pine," Mycologia, 1956, 48, 25-40. 3. Lilly, V. G. and Barnett, "Utilization of sugars by Fungi," Tech. Bull. West. Va. Univ., H.L. 1953, 362, 5-58. 4. Oddoux, L. "Utilization cornpar6e du sorbose et du fructose naturels Far une centaine d' Homobasideomycetes," Comp. Rer.d. Acad. ScL, 1952, 234, 654-57, 5. Pisano, M. A. and Plucker, "Effect of sorbose on the growth of Cephalosporium longb A.F, sporum," Mycologia. 1958. 50, 222-28. 234 K. $. BILGRAMI 6. Tandon, R. N. andBilgrami, "The utilization and synthesis of oligosaccharide~ by two K.S. species of Pestalotia," Prec. Natl. Inst. S~i., 1958, 24, 118-- 24. 7. "rattan, E. L., Baratt, R.W. "Chemical ind~uction of colonial paramorphs," S¢ience~ and Cutter, V. M., Jr. 1949, 19, 509-11.

* Original nol~ seen.