Actinomycetes University of Udine, Mycology Department ISSN: 0732-0574 Vol. 1, Num. 3, 1990, pp. 75-78

Streptomycetes Of Sandy Biotopes At Various Stages Of Natural Overgrowth

K.I.ANDREYUK, H.V.VALAGUROVA and K.A.MYATLIKOVA

Institute of Microbiology and Virology, Kiev, USSR

Code Number: AC90011
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Abstract.

Members of the genus Streptomyces play an important role in the contamination of lifeless sandy substrates. This is the result not only of their mycelial structure but also of their high ecological plasticity. Streptomycetes are characterized by a wide range of trophical abilities that permit them to adapt to various conditions of the environment and at the same time influence it. The ability of streptomycetes to synthesize biologically active compounds including antibiotics, vitamins and other metabolites permits them to serve as a factor regulating the composition of the microbial community at various stages of the primary succession of microbial coenosis.

Sands and sandy soils are wide spread in soil-climatic zones. On the banks of deep-water rivers even at present one can see the plots of flood-lands typical of the primary stages of soil formation.

Various microorganisms (Mycobacterium, Pseudomonas, Arthrobacter, Fungi) take an active part in the transformation of parent rock. There is insufficient information about streptomycetes (Sushkina and Gael, 1975; Avakyan et al., 1981; Forster et al., 1981; Parinkina, 1985).

The aim of this work was to study the streptomycete flora in sandy biotopes undergoing the various stages of natural overgrowth.

Materials And Methods

Samples. Samples of sandy substrates were collected at depths of 0-2 and 2-20 cm in plots with the successive ranges: 1) sand without vegetation; 2) sand partly covered with algae; 3) sand partly covered with moss-lichen associations; 4) primitive sandy soil under meadow phytocoenosis.

Isolation and counting of streptomycetes. Streptomycetes were isolated by spreading samples (water suspension 1:1,000,000) on solid nutrient media: peptone-beef agar for the forms utilizing organic nitrogen; starch-ammonium agar for the forms assimilating mineral nitrogen; water agar ("starvation-agar") and Eshby medium for oligotrophic forms; cellulose medium for cellulose-destroyers. The plates were incubated at 28 C for 7-10 days before the colonies were counted. Subcultures were made and checked for purity.

Qualitative study of isolates. Isolates were placed in series from the results of morphological observations and properties exhibited in the tests and media proposed by Shirling and Gottlieb (1966).

Streptomycetes influence on bacterial cultures. The influence of streptomycetes on the growth of a bacterial test- culture was determined by the block method (Gause et al., 1957). The most frequently occurring spore-forming bacterium, Bacillus sp., was used as the test-culture. The number of streptomycetes (antagonists and stimulators) was calculated as follows. A thin layer of peptone-beef agar, containing the test-culture cells, was poured into agar plates containing streptomycete colonies and then incubated for 2 days at 28 C. The amount of antagonistic and stimulating streptomycetes was estimated respectively from the number of zones without growth or with abundant growth.

Results And Discussion

Number and diversity of streptomycetes. The increase in amounts of microorganisms and the intensification of microbiological processes goes from lifeless sand to primary meadow soil through intermediate stages in the examined range of biotopes (Andreyuk et al., 1989).

Members of the genus Streptomyces were found to be very abundant in sandy substrates. From 14,000 to 6,000,000 million units were counted per gram of substrate (Table 1). As can be seen from this table the number of streptomycetes is rather variable and possibly depends on factors including season of the year, biotope property and depth of sample.

It is known that streptomycetes can assimilate various compounds due to their strong enzymatic system. The microbial communities of the examined biotopes, which are poor in nutrients, contained sufficient amounts of various compounds, simple and complex, for the streptomycetes to utilize (Table 2).

Table 1. Streptomycetes (10^3/g) in sandy biotopes.

Biotopes                   Layer   May    August  November 
                           (cm)
----------------------------------------------------------
Sand without vegetation    0-20    14.3    ND      127.6
Algal association          0-2     50.0    197.0    78.3
                           2-2    447.8    670.0    44.3
Moss-lichen association    0-2    170.4    277.0    63.0
                           2-20    60.1    113.0   200.0
Meadow phytocoenosis       0-2   6787.2   2411.7  6660.0
                           2-20  4159.4   4344.0  2700.0

Table 2. Streptomycetes (10^3/g and percentages) in microbial communities with different nutritional requirements.

Biotopes       Organic  Mineral  Nitrogen  Carbon    Cellulose 
               Nitrogen Nitrogen (minimal) (minimal) 
--------------------------------------------------------------
Sand without 
vegetation      25.2     47.3     76.5       72.7     0.03
               (24.9)   (17.3)   (14.7)     (21.6)   (5.0)
Algal 
association     79.4    359.4    299.8      192.5     7.6
               (42.9)   (61.6)   (46.3)     (38.3)  (97.0)
Moss-lichen 
association      7.6    128.9     20.8      151.4    15.1
                (1.7)   (21.5)    (3.7)     (18.4)   (68.3)
Meadow 
phytocoenosis  216.6   4510.4   1686.0     3300.0      6.1
                (3.9)   (21.5)    (7.7)      (9.6)   (32.8)

Primary producers selectively effect the development of the various microorganisms during the transformation of the surroundings. Algae, moss, lichens and grasses in the range of ecological biotopes examined serve as environment-builders.

A biotope in which algae serve as the edificator attracted our attention. The specific weight of streptomycetes in various trophical groups of microorganisms was quite high and reached 97% in the community of cellulose destroyers. Streptomycete contents in the next biotopes were less.

The discovery of streptomycetes with various trophical abilities at all stages of primary plant succession on alluvial sands shows the considerable role of these microorganisms in inhabiting sandy substrates. At the same time the diversity of streptomycete flora was small. The representatives were from no more than three series - White, Gray and Red.

The forms related to the Red series were found to be numerically dominant in the streptomycete community of sand without plants. The representatives of white streptomycetes (White series) prevailed in sandy substrate under algae; the members of the Red series were present in small amounts. Under a moss-lichen association streptomycetes were represented by forms with gray mycelium (Gray series) and minute amounts of red forms. The streptomycete flora under meadow vegetation was composed of forms of the White and Gray series.

Table 3. Influence of streptomycetes on culture

growth. (* + = stimulation, - = inhibition, 0 = no effect.

Average of five experiments).

        No.  Radius 
Series       (mm)* 
-------------------
Gray    1    +4.0 
        4    +3.0 
       12     0 
       14    -1.0 
       18    +4.0 
       19     0 
       29    +5.0 
       32    +5.0 
       35    -6.0 
       39    +4.0 
       45    -1.0 
White   7     0 
        8    -2.0 
       10    +5.0 
       23    -7.0 
Red    25     0 
       27    -2.0 
       28    -3.0 
       31     0 
       33    -1.0

Role of streptomycetes in communities. On the basis of streptomycete specific weight in microbial communities forming in the examined biotopes, it is possible to assume that these microorganisms are not just involved in substrate consumption (Table 2).Because of the potential capacity of streptomycetes and in particular of their ability to form various biological active compounds (Krassilnikov, 1950; Waksman, 1962; Andreyuk et al., 1974), one may suppose that they can exert some influence on other components of the newly forming microbial coenosis, for example on bacteria.

Twenty isolates of streptomycetes were tested for their activity against one of the most frequently occurring organism, Bacillus sp. (Table 3). Different effects were exerted by streptomycetes on the Bacillus. Parallel with the inhibition of the test-culture, also growth intensification was observed and in same cases a neutral reaction.

The data obtained on streptomycetes, inhibitors and stimulators, in the community assimilating mineral nitrogen are presented in Table 4. In sands without vegetation the streptomycete flora consisted of equal quantities of stimulators and antagonists, as regards Bacillus sp. A possible explanation of this fact could be that at this stage of organization the microorganism community is represented by casual microorganisms with unstable relations.

Table 4. Streptomycetes inhibitors and stimulators of Bacillus sp. in communities utilizing mineral nitrogen (10^3/g and percentages)

Biotopes            Inhibitors Stimulators    Ratio
----------------------------------------------------
Sand without           5.6        5.6           1:1 
vegetation           (50.0)     (50.0) 
Algal association    103.2       36.7         2.8:1 
                     (73.8)     (26.2)
Moss-lichen           16.6       56.6         0.6:1 
association          (38.4)     (61.6) 
Meadow               506.6     2465.0         0.2:1 
phytocoenosis        (17.0)     (83.0)

There were three times more antagonists than stimulators in the biotope with algae. In the moss-lichen biotope and in the meadow phytocoenosis this ratio was shifted towards increasing numbers of stimulator streptomycetes.

The results obtained are in accordance with the known state of general ecology (Odum, 1975; Rabotnov, 1983). There is a prevalence of competition and rivalry for nutritional sources in the pioneer organisms associations; during ecosystem formation such relations change to mutual aid and cooperation.

Thus as the biotope structure becomes more complicated by natural overgrowings of flood-lands, there is an accompanying change in qualitative streptomycete composition: the increase in the number of forms stimulating bacterial growth. The role of streptomycetes in examined biotopes is not limited by their reducing functions. They also play a role as regulating factors in the formation of microbial coenosis. The decrease in antagonistic streptomycetes numbers owing to the increase in stimulators shows the formation of microbial coenosis in the range of biotopes "sand without vegetation ---> algal synusia ---> moss-lichen association ---> meadow phytocoenosis".

Acknowledgments.

The authors acknowledge the assistance Mrs. Galina A. Tkacheva for technical help.

References

Andreyuk, E.I., E.V.Valagurova, E.A. Myatlikova, E.S.Gumenko & G.A. Tkacheva (1989). Microbial communities of sands on various stages of natural overgrowings. Microbiol.J., 51:8-12

Andreyuk, E.I., E.Viadimirova & S.B. Kogan (1974). Soil Actinomycetes of the South of the European Part of the USSR and their Biological Activities. Noukova Dumka, Kiev, 143 pp. (in Russian)

Avakyan, Z.A., G.I.Karavaiko, E.O.Melnikova, V.S.Krutsko & Yu.I. Ostroushko (1981). The role of microscopic fungi in the process of rock and minerals decay of pegmatite deposit. Mikrobiologia, 50:156-162 (in Russian)

Forster, S.M. & T.H.Nicolson (1981). Aggregation of sand from a maritime embryo sand dune by microorganisms and higher plants. Soil Biol.and Biochem., 13:199-203

Gause, G.F., T.P.Preobrazhenskaya, E.S. Kudrina, N.O.Blinov, I.D.Ryabova & M.A. Sveshnikova (1957). The aspects of Classification of Antagonistic Actinomycetes. Medgiz, Moscow, 208 pp. (in Russian)

Krassilnikov, N.A. (1950). Antagonistic Actinomycetes and Antibiotic Substances. Academic Press of the USSR, Moscow, 303 pp. (in Russian)

Odum. Eu.P. (1957). Fundamentals ,of Ecology. Mir, Moscow, 740 pp. (in Russian) Parinkina, O.M. (1985). Soil microflora in the process of vegetation of stripped soils of the various mechanical composition in Taimyr peninsula tundra. Ecologia, 1:29-35 (in Russian)

Rabotnov, T J.. (1983). Phytocenelogy. Moscow University Press, 2nd ed. (in Russian)

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

Sushkina, N.N. & A.G.Gael (1975). Microflora and soil formation on steppe sands. Vestnic of Moscow University. Biologia and Pochvovedenie, 2:83-90 (in Russian)

Waksman, S.A. (1962). The Actinomycetes. Williams & Wilkins Co., Baltimore, vol. 3.

Copyright 1990 C.E.T.A., The International Centre for Theoretical and Applied Ecology, Gorizia