Some ecological and physiological studies on bacteria isolated from salt-affected soils of Egypt
✍ Scribed by H. H. Zahran; Dr. A. M. Moharram; H. A. Mohammad
- Publisher
- John Wiley and Sons
- Year
- 1992
- Tongue
- English
- Weight
- 497 KB
- Volume
- 32
- Category
- Article
- ISSN
- 0233-111X
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✦ Synopsis
Members of Bricillcicecir, Rlzi=ohioceae, actinomyeetes and others were isolated from cultivated and non-cultivated saline soils. The high population of bacteria and actinomycetes were almost coincided with the relatively high levels of organic matter whatever the degree of soil salinity.
Bacilhrs . s ~~~r o i h ~r i ) ~~p i z ; / u ~s
and B. suhrilis wese more frequently isolated than other Bucil/~i.s species. Most of Rhi:obiuni isolates were salt tolerant being able to grow in media containing 3% and 6 % NaCI. The abilities of different bacterial isolates to attack citrus pectin. soluble and insoluble forms of cellulose were also tested.
Soil microorganisms are usually subjected to variable ecological and nutritional factors including salinity levels, availability of organic matter, soil moisture content ere. which affect their growth and activity. In Egypt. the estimated area of salt-affected soils have dramatically increased not only due to the usage of salt-contaminated irrigation water of the River Nile (EL-GIBALY 1977) but also as a result of bad drainage management. The recent official reports of the Egyptian authorities estimated the salt-affected cultivated lands to be about. 1.875 million acrs. The continuous physicochemical and microbial analysis of these soils is undoubtedly very important in the projects aiming to improve soil fertility and productivity. This work represents a trial to shed some lights on the bacterial populations and some enzymatic activities of certain species commonly found in the salt-affected soils.
Methods
Physico-chemical characteristics of soil samples: The soil samples ( 18 samples from salt-affectcd soils from cultivated and non-cultivated fields) were analyzed physically and chemically to determine their-pH values, moisture and organic matter contents. total salinity, electric conductivity. the levels of some cations (Ca". Mg+', K + , Na') and anions (HCO; and CI-) using the methods described in JACKSON (1958). In case of N a + and K'. the flame emission technique (WILI.IAMS 1960) was employed.
Bacteriological analysis of soil samples:
A) Estimation of total viable counts: Bacterial counts (cells! gram dry soil) were estimated using the dilution plate method and the following medium types. a. Nutrient agar (NA) supplcn~cnted with 3% NaCl to allow the growth of different halophilie and halotolerant bacteria. b. Arginine glycerol salt medium (AGS) for actinomycetes which contained (g/l): glycerol, 2.0; 1.-arginine, 0.25; NaCI. 0.1 ; CaCO,, 0.01 ; MgSO, . 7H,O, 0.01; FeSO,, 0.01; agar-agar. 20.0 (EL-NAKEEB and LECHEVALIER 1963).
B) Identification of BrrciN~u species: The macroscopic appearance. microscopic characters (shape and size of cells, shape and location of mature endosposes), rcaction to GRAM'S stain in addition to the different biochemical activities were used to ensure good identifications of Bacillus species in the light of the scheme, given by BUCHANAN and GIBBONS ( 1974) and GORDON et a/. (1973).
C) Isolation of Rhizobia from saline soils: The method described by CARPENTER and ROBERTSON (1983) was used to isolate Rliizohi~rin species from root nodules of some leguminous plants (lupin,