Related Experiment Video
Updated: Aug 10, 2026
08:21
Site-specific Bacterial Chromosome Engineering: ΦC31 Integrase Mediated Cassette Exchange (IMCE)
Published on: March 16, 2012
Reversible transition between active and dormant microbial states in soil
J Stenström1, K Svensson, M Johansson
1Department of Microbiology, Swedish University of Agricultural Sciences, P.O. Box 7025, SE-750 07, Uppsala, Sweden
FEMS Microbiology Ecology
|July 14, 2001
Summary
Soil microbial respiration involves growing (r) and non-growing (K) states, with substrate availability dictating their proportions. Glucose addition rapidly shifts microbes to the active (r) state, which then slowly reverts to the dormant (K) state over weeks.
Area of Science:
- Soil Microbiology
- Biogeochemical Cycles
- Microbial Ecology
Background:
- Substrate-induced respiration (SIR) quantifies microbial activity, differentiating between growing (r) and non-growing (K) biomass fractions.
- The proportion of r and K microorganisms in soil is influenced by substrate availability, suggesting dynamic transitions.
- Understanding these transitions is crucial for soil carbon cycling and nutrient dynamics.
Purpose of the Study:
- To investigate the reversibility and dynamics of transitions between growing (r) and non-growing (K) microbial states in soil.
- To determine the influence of substrate availability (glucose) and pre-incubation time on these microbial state shifts.
- To test hypotheses regarding substrate-driven reversible transitions and community-level controls on microbial growth.
Main Methods:
- Addition of varying glucose concentrations to three different soils with four pre-incubation times (4-46 days).
- Measurement of respiration rates using the substrate-induced respiration (SIR) method.
- Correction for abiotic CO(2) flush and analysis of CO(2)-C mineralization kinetics.
Main Results:
- Glucose addition rapidly increased respiration (SIR), indicating a shift from non-growing (K) to growing (r) states.
- This elevated respiration reverted to baseline levels within 27-46 days, demonstrating a slow back-transition from r to K.
- The rate of K to r transition correlated with initial glucose concentration, while the back-transition half-lives varied among soils (12-70 days).
Conclusions:
- Soil microbial biomass dynamics involve reversible oscillations between active (r) and dormant (K) physiological states.
- Microbial specific activity responds sharply to substrate availability, transitioning between dormant and fully active states rather than continuously.
- Community-level controls appear to regulate growth, potentially inhibiting it until the biomass is fully in the active (r) state.
Related Concept Videos
01:26Transformation
Microbial communities are dynamic environments where cell lysis releases free DNA into the surroundings. Other cells can take up this extracellular DNA through a process known as transformation.When a cell incorporates this foreign DNA into its genome, resulting in genetic modification, the process is known as transformation. Cells capable of this process are termed competent. Competence can be natural, as observed in certain bacteria and archaea, or artificially induced in the...
01:16Transduction
Among the three main modes of HGT—transformation, conjugation, and transduction—transduction is unique in that it is mediated by bacteriophages, or bacterial viruses.Transduction occurs in two ways. Generalized transduction occurs during the lytic cycle of a bacteriophage infection. In this process, bacteriophages infect bacterial cells, replicate within them, and ultimately cause cell lysis, releasing newly assembled virions. Occasionally, random fragments of the bacterial genome are...
01:16Viral Replication: Lysogenic Cycle
The lysogenic cycle is a crucial viral replication strategy that allows bacteriophages to persist within host cells without immediately destroying them. This process is primarily observed in temperate phages, such as bacteriophage lambda (λ), which infects Escherichia coli. The cycle allows the viral genome to persist across bacterial generations while keeping host cells viable.Integration of the Viral GenomeUpon infection, bacteriophage lambda attaches to the bacterial surface and injects its...
01:25Microbial Interactions: Mutualism
Mutualism is a symbiotic interaction in which all participating organisms benefit. These relationships can be obligate or facultative and are fundamental to ecosystem functions across diverse biological systems.Plant–Fungi MutualismOne well-known example is the association between plant roots and mycorrhizal fungi, such as Rhizophagus species. The fungal hyphae penetrate the root hairs and the epidermis, forming an extensive hyphal network that establishes a symbiotic association. Through this...
01:26Microbial Interactions: Cooperation
Microbial cooperation involves beneficial interactions in which different species work together for individual or mutual advantage. These interactions can profoundly influence ecological dynamics and evolutionary processes, and they are essential to many pathogenic and symbiotic relationships.Nematode–Bacteria CooperationA striking example is the relationship between the Gram-negative bacterium Xenorhabdus nematophila and the parasitic nematode Steinernema carpocapsae. Juvenile nematodes...
01:24iChip
The cultivation of environmental microorganisms has long been hindered by the inability to replicate complex native conditions in vitro. The isolation chip (iChip) addresses this limitation by facilitating the growth of previously uncultivable microorganisms through in situ incubation. Designed for high-throughput microbial cultivation, the iChip comprises hundreds of microchambers, each capable of housing a single microbial cell. These microchambers are loaded with a mixture of molten agar and...