Culturability as an indicator of succession in microbial communities

• Published in: Microbial ecology Vol. 42; no. 2; pp. 150 - 158
• Main Authors: Garland, J.L, Cook, K.L, Adams, J.L, Kerkhof, L
• Format: Journal Article
• Language: English
• Published: Legacy CDMS Springer-Verlag New York Inc 01.08.2001; Springer; Springer Nature B.V
• Subjects: acridine orange; agar; Agronomy. Soil science and plant productions; Amino acids; Amino Acids - pharmacokinetics; Animal, plant and microbial ecology; Applied ecology; Bacteria; Bacteria - growth & development; Bacteria - metabolism; Biological and medical sciences; Biomass; Bioreactors; Cell culture techniques; Colony Count, Microbial; Community structure; Cultured cells; DNA; Ecology; Economic plant physiology; Ecosystem; Ecotoxicology, biological effects of pollution; energy; Environment, Controlled; Fundamental and applied biological sciences. Psychology; Hydroponics; Life Sciences (General); Microbial activity; microbial communities; Microorganisms; Plant growth; Plant Roots - growth & development; Plant Roots - metabolism; Plant Roots - microbiology; Plants; reproduction; Rhizosphere; Space life sciences; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); Terrestrial environment, soil, air; Time Factors; Triticum - growth & development; Triticum - metabolism; Triticum - microbiology; Water Microbiology; Wheat; Nasa Center Ksc; Nasa Discipline Life Support Systems; Monocotyledones; Theory; Microcosm; Agar; Orange; Rhizosphere; Reproduction; Gramineae; Chlorides; Angiospermae; Bacteria; Colony; Niche; Spermatophyta; Wheat; Microbial community; Triticum aestivum; NASA Center KSC; NASA Discipline Life Support Systems
• ISSN: 0095-3628; 1432-184X
• DOI: 10.1007/s00248-001-0002-3

Successional theory predicts that opportunistic species with high investment of energy in reproduction and wide niche width will be replaced by equilibrium species with relatively higher investment of energy in maintenance and narrower niche width as communities develop. Since the ability to rapidly grow into a detectable colony on nonselective agar medium could be considered as characteristic of opportunistic types of bacteria, the percentage of culturable cells may be an indicator of successional state in microbial communities. The ratios of culturable cells (colony forming units on R2A agar) to total cells (acridine orange direct microscopic counts) and culturable cells to active cells (reduction of 5-cyano-2,3-ditolyl tetrazolium chloride) were measured over time in two types of laboratory microcosms (the rhizosphere of hydroponically grown wheat and aerobic, continuously stirred tank reactors containing plant biomass) to determine the effectiveness of culturability as an index of successional state. The culturable cell:total cell ratio in the rhizosphere decreased from approximately 0.25 to less than 0.05 during the first 30-50 days of plant growth, and from 0.65 to 0.14 during the first 7 days of operation of the bioreactor. The culturable cell:active cell ratio followed similar trends, but the values were consistently greater than the culturable cell:total cell ratio, and even exceeded 1 in early samples. Follow-up studies used a cultivation-independent method, terminal restriction fragment length polymorphisms (TRFLP) from whole community DNA, to assess community structure. The number of TRFLP peaks increased with time, while the number of culturable types did not, indicating that the general decrease in culturability is associated with a shift in community structure. The ratio of respired to assimilated 14C-labeled amino acids increased with the age of rhizosphere communities, supporting the hypothesis that a shift in resource allocation from growth to maintenance occurs with time. Results from this work indicate that the percentage of culturable cells may be a useful method for assessing the successional state of microbial communities.