Rapid Method of Determining Factors Limiting Bacterial Growth in Soil

Abstract

A technique to determine which nutrients limit bacterial growth in soil was developed. The method was based on measuring the thymidine incorporation rate of bacteria after the addition of C, N, and P in different combinations to soil samples. First, the thymidine incorporation method was tested in two different soils: an agricultural soil and a forest humus soil. Carbon (as glucose) was found to be the limiting substance for bacterial growth in both of these soils. The effect of adding different amounts of nutrients was studied, and tests were performed to determine whether the additions affected the soil pH and subsequent bacterial activity. The incubation time required to detect bacterial growth after adding substrate to the soil was also evaluated. Second, the method was used in experiments in which three different size fractions of straw (1 to 2, 0.25 to 1, and <0.25 mm) were mixed into the agricultural soil in order to induce N limitation for bacterial growth. When the straw fraction was small enough (<0.25 mm), N became the limiting nutrient for bacterial growth after about 3 weeks. After the addition of the larger straw fractions (1 to 2 and 0.25 to 1 mm), the soil bacteria were C limited throughout the incubation period (10 weeks), although an increase in the thymidine incorporation rate after the addition of C and N together compared with adding them separately was seen in the sample containing the size fraction from 0.25 to 1 mm. Third, soils from high-pH, limestone-rich areas were examined. P limitation was observed in one of these soils, while tendencies toward P limitation were seen in some of the other soils.

Seasonality and resource availability control bacterial and archaeal communities in soils of a temperate beech forest

“…Seasonal changes in soil climate were further closely linked to short-and medium-term variations in resource availability, which further correlated with the quantity and quality of organic matter entering the soil, as it was also previously suggested (Bell et al, 2009;Cookson et al, 2006;Krave et al, 2002). Consequently, total bacterial communities and individual phyla studied were clearly shaped by supply of DOC, DON and mineral N (that is, ammonia, nitrate), which is in agreement with previously published data (Drenovsky et al, 2004;Zak et al, 2003;Alden et al, 2001).…”

Monitoring of the microbial community composition in saline aquifers during CO2 storage by fluorescence in situ hybridisation

“…2). It has been generally accepted that carbon availability and environmental conditions are controlling microbial growth (Aldén et al, 2001;Brockman et al, 1992;Fredrickson and Balkwill, 2006;Fry et al, 1997;Jørgensen and Boetius, 2007;Whitman et al, 1998). Analyses of the organic acids in the fluids revealed that acetate seems to be the major constituent of the dissolved organic carbon (DOC).…”

Transcriptional and antagonistic responses of Pseudomonas fluorescens Pf0-1 to phylogenetically different bacterial competitors

“…Most known soil bacterial species are organotrophs that is, they obtain the energy for growth from the assimilation of organic compounds. However, the availability or accessibility of degradable organic compounds is limited in most soils (Alden et al, 2001;Demoling et al, 2007). In addition, there is a high degree of overlap in metabolic abilities of organotrophic bacteria (Strickland et al, 2009).…”