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Colony Growth Rate (colony + growth_rate)
Selected AbstractsModelling the combined effect of temperature, pH and aw on the growth rate of Monascus ruber, a heat-resistant fungus isolated from green table olivesJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2003E.Z. Panagou Abstract Aims: Growth modes predicting the effect of pH (3·5,5·0), NaCl (2,10%), i.e. aw (0·937,0·970) and temperature (20,40°C) on the colony growth rate of Monascus ruber, a fungus isolated from thermally-processed olives of the Conservolea variety, were developed on a solid culture medium. Methods and Results: Fungal growth was measured as colony diameter on a daily basis. The primary predictive model of Baranyi was used to fit the growth data and estimate the maximum specific growth rates. Combined secondary predictive models were developed and comparatively evaluated based on polynomial, Davey, gamma concept and Rosso equations. The data-set was fitted successfully in all models. However, models with biological interpretable parameters (gamma concept and Rosso equation) were highly rated compared with the polynomial equation and Davey model and gave realistic cardinal pHs, temperatures and aw. Conclusions: The combined effect of temperature, pH and aw on growth responses of M. ruber could be satisfactorily predicted under the current experimental conditions, and the models examined could serve as tools for this purpose. Significance and Impact of the Study: The results can be successfully employed by the industry to predict the extent of fungal growth on table olives. [source] Effect of hot-water treatments in vitro on conidial germination and mycelial growth of grapevine trunk pathogensANNALS OF APPLIED BIOLOGY, Issue 2 2010D. Gramaje In this study, the sensitivity of Cadophora luteo-olivacea, Cylindrocarpon liriodendri, Cn. macrodidymum and eight species of the genus Phaeoacremonium to hot-water treatments (HWTs) in vitro was evaluated. Conidial suspensions and plugs of agar with mycelia were placed in Eppendorf vials and incubated for 30, 45 or 60 min in a hot-water bath at 41, 42, 43, 44, 45, 46, 47, 48 or 49°C for Cylindrocarpon spp. and at 49, 50, 51, 52, 53, 54 or 55°C for Ca. luteo-olivacea and Phaeoacremonium spp. In general, conidial germination and the colony growth rate of all pathogens decreased with increased temperature and time combinations. Cylindrocarpon spp. were more sensitive than Ca. luteo-olivacea and Phaeoacremonium spp. to HWT temperatures. Conidial germination of Ca. luteo-olivacea was inhibited by treatments above 51°C,30 min, while treatments up to 54°C,60 min were necessary to inhibit the mycelial growth. For Cylindrocarpon spp., conidial germination was inhibited by treatments above 45°C,45 min, while treatments above 48°C,45 min were necessary to inhibit the mycelial growth. Regarding Phaeoacremonium spp., treatments up to 54°C,60 min were necessary to completely inhibit both conidial germination and mycelial growth. These results suggest that current HWT protocols at 50°C for 30 min may be sufficient to control Cylindrocarpon spp. However, it would be necessary to develop HWT using higher temperatures to reduce the incidence of Ca. luteo-olivacea and Phaeoacremonium spp. infections. [source] Mechanisms of population regulation in the fire ant Solenopsis invicta: an experimental studyJOURNAL OF ANIMAL ECOLOGY, Issue 3 2001Eldridge S. Adams Summary 1We tested for density-dependent regulation of biomass in a population of the fire ant Solenopsis invicta and examined the mechanisms of population recovery following replicated colony removals. 2,All colonies were killed within the core area (1018 m2) of six plots, while six additional plots served as undisturbed controls. Over the next 5 years, colonies were mapped several times per year and the biomass of each colony was estimated from the volume of the nest-mound. 3,The average biomass and density of colonies within the removal areas gradually converged on those of control plots and were no longer detectably different after two years. Thereafter, ant biomass on experimental and control plots showed nearly identical seasonal and yearly fluctuations. 4Territories of colonies surrounding the removal areas rapidly expanded following the deaths of neighbours, while average territory size on control plots showed little short-term change. 5,Significantly more new colonies were established within core areas of experimental plots than within core areas of control plots during the first year following removals. 6,The per-colony probability of movement and the net influx of colony biomass were significantly higher in central regions of the experimental plots than in control plots during the first year. The directions of colony movements were clustered towards the centres of experimental plots in the first 2 years, but did not show significant directional trends on control plots. 7,In all 5 years of the study, annual mortality rates were lower for larger colonies, but the size-specific risk of mortality was not significantly affected by the experimental removal of competitors. 8,The growth rates of colonies, adjusted for initial size, were significantly higher in central regions of experimental plots than in control plots during the first two years of the study. In all years, colony growth rates declined with increasing colony size. 9,These results indicate that populations of S. invicta are regulated by competition among neighbouring colonies. Due to large intraspecific variation in colony size, the dynamics of ant populations are described more accurately by measures of total ant biomass than by colony density alone. [source] Persisting Hyper-abundance of Leaf-cutting Ants (Atta spp.) at the Edge of an Old Atlantic Forest FragmentBIOTROPICA, Issue 6 2009Sebastian T. Meyer ABSTRACT Leaf-cutting ants (LCAs) profoundly benefit from edge creation in Neotropical forests, where they act as a keystone species and disturbance agent. In view of their poorly explored population dynamics, the question arises whether high densities of LCAs are a transitional or a persisting phenomenon. We studied the temporal variation of LCA colony densities at the edge of the Brazilian Atlantic forest. At physically stable edges of an old forest fragment, densities of Atta cephalotes and Atta sexdens (11 and five times higher in a 50 m edge zone in comparison with the forest interior) persisted over a 4-yr interval (2001,2005) with no significant difference in densities between years. Species-specific per colony growth rates ranged from 12 to ,5 percent/yr, suggesting that populations were approximately at equilibrium. High rates of colony turnover (little less than 50% in 4 yr) indicated an average colony life span of about 7 yr,a life expectancy considerably lower than previous estimates for Atta colonies. Stable, hyper-abundant populations of LCAs accord with the constantly high availability of palatable pioneer vegetation (the preferred food source of LCAs) at forest edges and are expected to persist in time as long as forests are characterized by high edge to interior ratios, with potentially long-lasting consequences for the ecosystem. [source] | ||||||||||