Effects of zinc-smelter emissions on forest soil microflora

Abstract

Within 2 km of a zinc (Zn) smelter in Palmerton, Pennsylvania, near the Lehigh Water Gap, up to 13.5% Zn by weight has been measured in the O2 horizon of the soil, and up to 8% Zn in the A1 horizon. The total numbers of bacteria, actinomycetes, and fungi (measured by dilution plate counts) were greatly reduced in the most severely Zn-contaminated soils compared with control soils. The reduction of microbial populations may be a partial cause of the decreased rate of litter decomposition at Lehigh Gap. Growth of most bacteria from control sites was reduced by 100 to 200 muM Zn, most actinomycetes by 100 muM Zn, and most fungi by 100 to 1000 muM Zn in thin-Pablum extract agar (TPab). All the tested actinomycetes and non-spore-forming bacteria isolated from Zn-contaminated Lehigh Gap soils were Zn-tolerant, growing normally in media containing 600-2000 muM Zn. Most fungi, regardless of source, were capable of at least 50% of normal growth at 700 muM Zn. Zinc-tolerant bacteria, actinomycetes, and fungi were readily isolated from low-Zn soils, suggesting that selection for Zn tolerance may proceed rapidly. Acidophilic Mortierella species have been selectively eliminated near the smelter, apparently because of elevated soil pH. Peryronellaea glomerata (Corda) Goidanich and Coniothyrium spp. were found only in the high-Zn soils.

Role of soil rhizobacteria in phytoremediation of heavy metal contaminated soils

“…Experiments showed that the number of bacteria in the rhizosphere of (Brookes and McGrath, 1984;Chander and Brookes, 1991;Jordan and LeChevalier, 1975;Konopka et al, 1999). Besides, the microorganism community structure of the rhizosphere population is important in the context of plant growth.…”

Fungos anamorfos do solo da região dos lagos no Município de Santa Gertrudes, SP, Brasil

“…Nas concentrações inferiores a 100 µM, o zinco é considerado elemento essencial para o crescimento de fungos (Ross 1975). A partir desta dosagem, o zinco geralmente causa efeitos prejudiciais acentuados sobre a vegetação e a microbiota (Jordan & Lechevalier 1975).…”

“…O efeito seletivo dos metais pode resultar na substituição de diversas espécies e no estabelecimento de uma micota terrestre resistente ou tolerante (Jordan & Lechevalier 1975). A presença de determinado metal no solo representa, assim, mais um parâmetro a ser levado em consideração na compreensão das interações competitivas que contribuem para a composição da micota terrestre.…”

Effect of Metals Contamination on Soil Microbial Diversity, Enzymatic Activity, Organic Matter Decomposition and Nitrogen Mineralisation (A Review)

“…Huysman et al, 1994). Jordan and Lechevalier (1975) found a decrease of between one to two orders of magnitude in numbers of bacteria along a Zn pollution gradient while fungi and actinomycetes were less affected. Dar (1996) studied the effect of added Cd and found greater diversity of fungi and higher bacterial populations in control than in the Cd treated soil.…”

“…Some species might be eliminated while others may appear in larger numbers because of reduced competition for substrate. Jordan and Lechevalier (1975) reported that microbial populations in soils close to a zinc-smelter contained greater proportions of bacteria able to grow on media containing high concentration of Zn. Several authors have found that, within the bacterial community, metals are more toxic to Gram-positive than the Gram-negative bacteria (Barkay et al, 1985).…”