The impact of combinatorial stress on the growth dynamics and metabolome of Burkholderia mesoacidophila demonstrates the complexity of tolerance mechanisms.

AIMS: The recently sequenced Burkholderia mesoacidophila (previously Pseudomonas mesoacidophila) is a soil organism and as such will be exposed to multiple concurrent stresses in the natural environment. The combinatorial stress potentially experienced by microbes in soil has not been investigated in detail. METHODS AND RESULTS: The impact of combinatorial stress on growth was investigated using tripartite variables-temperature, nutritional environment and either osmotic or oxidative stress. In nutritionally stringent conditions, increasing diamide concentration had no effect on growth while increasing H2 O2 concentration reduced both growth rate and maximum density. Metabolomic studies with oxidative stress revealed specific (unidentified) metabolites associated with diamide tolerance, and an overwhelming dominance of sugars and sugar alcohols in nutritionally stringent conditions with and without the additional stressor. CONCLUSIONS: Combinatorial stress tolerance is complex. Temperature had the greatest independent impact on growth, while the impact of the nutritional environment played a key role in oxidative stress tolerance. In nutritionally stringent conditions, the metabolome suggested different tolerance mechanisms for different types of oxidative stress. SIGNIFICANCE AND IMPACT OF THE STUDY: This work demonstrates the specificity of the stress response, and the need to consider multiple environmental factors to meaningfully investigate tolerance. Both environmental and clinical settings subject bacteria to combinatorial stress and this should be considered in the design of further studies.

The fungus that came in from the cold: dry rot's pre-adapted ability to invade buildings.

Many organisms benefit from being pre-adapted to niches shaped by human activity, and have successfully invaded man-made habitats. One such species is the dry rot fungus Serpula lacrymans, which has a wide distribution in buildings in temperate and boreal regions, where it decomposes coniferous construction wood. Comparative genomic analyses and growth experiments using this species and its wild relatives revealed that S. lacrymans evolved a very effective brown rot decay compared to its wild relatives, enabling an extremely rapid decay in buildings under suitable conditions. Adaptations in intracellular transport machineries promoting hyphal growth, and nutrient and water transport may explain why it is has become a successful invader of timber in houses. Further, we demonstrate that S. lacrymans has poor combative ability in our experimental setup, compared to other brown rot fungi. In sheltered indoor conditions, the dry rot fungus may have limited encounters with other wood decay fungi compared to its wild relatives. Overall, our analyses indicate that the dry rot fungus is an ecological specialist with poor combative ability against other fungi.

Interdependence of Primary Metabolism and Xenobiotic Mitigation Characterizes the Proteome of Bjerkandera adusta during Wood Decomposition.

The aim of the current work was to identify key features of the fungal proteome involved in the active decay of beechwood blocks by the white rot fungus Bjerkandera adusta at 20°C and 24°C. A combination of protein and domain analyses ensured a high level of annotation, which revealed that while the variation in the proteins identified was high between replicates, there was a considerable degree of functional conservation between the two temperatures. Further analysis revealed differences in the pathways and processes employed by the fungus at the different temperatures, particularly in relation to nutrient acquisition and xenobiotic mitigation. Key features showing temperature-dependent variation in mechanisms for both lignocellulose decomposition and sugar utilization were found, alongside differences in the enzymes involved in mitigation against damage caused by toxic phenolic compounds and oxidative stress.IMPORTANCE This work was conducted using the wood decay fungus B. adusta, grown on solid wood blocks to closely mimic the natural environment, and gives greater insight into the proteome of an important environmental fungus during active decay. We show that a change in incubation temperature from 20°C to 24°C altered the protein profile. Proteomic studies in the field of white-rotting basidiomycetes have thus far been hampered by poor annotation of protein databases, with a large proportion of proteins simply with unknown function. This study was enhanced by extensive protein domain analysis, enabling a higher level of functional assignment and greater understanding of the proteome composition. This work revealed a strong interdependence of the primary process of nutrient acquisition and specialized metabolic processes for the detoxification of plant extractives and the phenolic breakdown products of lignocellulose.

Determination of reactor biomass by acoustic resonance densitometry.

Acoustic resonance densitometry (ARD) is reported as a method suitable not only for precise investigations into changes of specific gravity in bioreactor media but also as a technique able to provide an accurate wide range and direct determination of cellular mass in fermentation processes. It is further shown that this method can replace present optical procedures, minimizing dilution errors and operator involvement and is suitable for development as an on-line biomass monitoring system.

The development and application of biosensing devices for bioreactor monitoring and control.

Presently, few of the reported (bio)chemical sensor devices have found application in fermentation monitoring and control. Although many devices with desirable selectivities have been reported, few have demonstrated reliability sufficient to encourage significant and widespread application. Chemical sensors (ion-selective electrodes, amperometric detectors, piezoelectric, field-effect transistors, semiconductor, Optrode and optoelectronic sensors), biosensors (based on potentiometric, amperometric, field-effect transistor and conductiometric detectors) and physical detection methods are reviewed with the aim of highlighting the problems of their application in this area. Physical detection principles appear to show promise as reliable and direct monitoring principles. However, even the more reliable discrete (bio)chemical sensor devices require the development of on-line flow sampling and autocalibration methods to demonstrate the necessary reliability. Biosensor devices appear most problematical and it is concluded that continued development of more direct biosensing principles is likely to prove most fruitful.

Self-management of nutrition.

Eleven overweight subjects received a behavioral treatment program for weight loss and a nutritional self-management program during a 10-week treatment period. The nutritional self-management program was evaluated using a multiple-baseline across-groups design. The results indicated that caloric restriction without the nutritional self-management program did not result in the consumption of a well-balanced diet. Introduction of the nutritional self-management program led to improvement of nutritional consumption across six food groups. Self-control of caloric intake within certain food groups, i.e., fruit and vegetable, was better than for others. These findings are discussed in terms of the methodological difficulties involved in managing nutrition and the significance of nutritional self-management for health problems other than obesity.