John W. Palfreyman

Extracellular phenoloxidase and peroxidase enzyme production during interspecific fungal interactions

Extracellular phenoloxidase enzymes have been implicated in the offensive/defensive strategies employed by fungi during interactions. To determine whether these enzymes are involved during Basidiomycete confrontations, a number of pairings between two brown-rot Basidiomycetes (Serpula lacrymans and Coniophora puteana) and several Deuteromycetes (Trichoderma spp. and Scytalidium FY) were performed. Laccase production was observed in pure cultures of C. puteana and Scytalidium FY, and in the interactions involving these two species. Laccase was also detected in the interactions involving S. lacrymans and all three Trichoderma isolates, although not in the respective pure cultures. Tyrosinase release was observed most frequently in interactions involving T. harzianum SIWT 25, although all other species also released tyrosinase under certain conditions, and peroxidase release was detected during all interspecific interactions. One exception involved T. viride SIWT 110 as this fungus did not produce tyrosinase under the experimental parameters utilized, and peroxidase release was inhibited during self-pairings and pairings involving the two other Trichoderma isolates. Extracellular laccase and tyrosinase production was much less on a low nutrient medium, although peroxidase production was not affected as strongly.

Factors Influencing Theoretical Knowledge and Practical Skill Acquisition in Student Nurses: An Empirical Experiment.

A previous qualitative study [Nurse Education Today 20 (2000) 499] investigated perceptions of nurse teachers, student nurses and preceptors of the theory-practice gap said to exist within nursing. One theme was views of how the theory-practice gap could be closed. A subsequent quantitative study is reported here, in which this theme was translated into three factors. A full factorial experimental design was used to study the effect of these factors on theoretical knowledge and practical skill acquisition in a sample of first year undergraduate student nurses from one institution of higher education (n=19). The effect of whether a nurse teacher or preceptor taught students theoretical elements relating to a clinical specialty, whether the nurse teacher and preceptor collaborated on the content of what was taught to students and whether students went straight to, or delayed the clinical specialty following theoretical input, was examined. The results demonstrated preceptors were more effective than nurse teachers in promoting theoretical knowledge relating to their clinical specialty. Collaboration between the preceptors and nurse teachers on teaching content was ineffective at increasing theoretical knowledge. Delay between theoretical input and clinical experience was not detrimental for medical placements and for rehabilitation placements, resulted in an improved theoretical knowledge.

Molecular analysis of intraspecific variation between building and ‘wild’ isolates of Serpula lacrymans and their relatedness to S. himantioides

Relationships between Serpula lacrymans and S. himantioides isolates of ‘wild’ Himalayan woodland and building (European and Australian) origin were examined using RAPD-PCR and ITS rDNA sequence comparison. GelCompar analysis of the genetic fingerprints of eighteen isolates using four RAPD-primer combinations clearly distinguished S. lacrymans and S. himantioides. Little intraspecific variation was observed in S. lacrymans (including isolates of Himalayan woodland origin), relative to S. himantioides. Despite previously reported differences in growth rates and decay capabilities of ‘wild’ Himalayan woodland S. lacrymans isolates and those from buildings, RAPD fingerprints and ITS sequences indicated they were genetically similar. Interspecific ITS sequence polymorphisms were consistent with other studies and clearly demonstrated S. himantioides and S. lacrymans were distinct taxa. Evolutionary questions regarding the origins of S. lacrymans are discussed.

Biological control of the dry rot fungus Serpula lacrymans by Trichoderma species: the effects of complex and synthetic media on interaction and hyphal extension rates

Abstract Using a standard medium (malt extract agar) and a minimal essential medium designed to mimic the carbon: nitrogen ratio in wood, a number of Trichoderma isolates were screened for their ability to kill Serpula lacrymans . From the results one Trichoderma species, T. harzianum 25, proved to be the most efficient at killing S. lacrymans . In addition, modifications to the nitrogen and iron concentrations of the minimal medium provided indications that the level of these two elements could prove important in the biological control of the dry rot fungus in wood.

Some aspects of interrelations between fungi and other biota in forest soil

Interrelations of fungal mycelium with other soil biota are of paramount importance in forestry and soil ecology. Here we present the results of statistical analysis of a comprehensive data set collected in the first (and the only) British fungus sanctuary over a period of four months. The variables studied included a number of soil properties, bacteria, protozoan flagellates, ciliates and amoebae, microbial and plant feeding nematodes, various microarthropods, and two fungal biomarkers--glomalin and ergosterol. One way ANOVA showed that the dynamics of the microbiota studied was influenced by seasonal changes. Superimposed on these changes, however, was variability due to biological interactions and habitat characteristics. Two fungal biomarkers, ergosterol and glomalin, were differently influenced by other biota and abiotic variables. The results indicate that the dynamics of soil fungi is influenced not only by soil microarthropods, but also by those found in forest litter. The overall outcome, therefore, is likely to be very complex and will depend upon specific conditions of any particular ecosystem.

The effect of calcium ion concentration on the growth and decay capacity of Serpula lacrymans (Schumacher ex. Fr.) Gray and Coniophora puteana (Schumacher ex. Fr.) Karst

The growth rates, decay capacity and acid production of Serpula lacrymans (Schumacher ex Fr.) Gray and Coniophora puteana (Schumacher ex Fr.) Karst. were monitored under experimental conditions by cultivating these organisms on a range of media supplemented with varying concentrations of calcium and other divalent metal ions. Both C.puteana and S.lacrymans had maximal growth rates when cultivated on malt extract agar and wood blocks incubated on this medium gave substantial decay rates. By contrast, C.puteana cultivated on minimal medium supplemented with 21 mM calcium gave reduced growth rates whilst intermediate concentrations of calcium had little effect on the growth of the organism. In all cases, C.puteana cultivated on calcium containing minimal media gave minimal decay of the wood blocks. Finally C.puteana acidified all media and no indication of buffering was observed. Results obtained from S.lacrymans demonstrated that increasing calcium nitrate concentration promoted decay of wood blocks and increased organism growth rates. S.lacrymans also acidifed the various media used, but surface pH profiles indicated that the organism was able to buffer acid production to a certain extent when calcium nitrate, or other divalent ions, were available.

The impact of current research on the treatment of infestations by the dry rot fungus Serpula lacrymans

There have been a number of advances in the understanding of the physiology of the dry rot fungus, Serpula lacrymans, in the last decade. Specifically, studies on the natural origins of the fungus, morphogenesis, toxicant tolerance, environmental sensitivity, nitrogen metabolism, utilization of non-woody materials and biological control have all contributed to this understanding and each is discussed in relation to potential control strategies for the future. In addition, molecular studies involving detection, monitoring of speciation and the heat shock response of Serpula lacrymans have provided new insights into an organism which is uniquely destructive in the built environment.

Some aspects of complex interactions involving soil mesofauna: analysis of the results from a Scottish woodland

Stepwise regression modelling and canonical correspondence analysis were used to analyse data on soil properties and the abundance of soil mesofauna collected from a woodland typical of the Borders of Scotland. The pattern of relationships revealed by stepwise regression models was different for each month, and the models compiled on the overall dataset were generally weaker than those compiled for separate months. Functional relationships among different microarthropods revealed by stepwise regression modelling are summarised in a structural model of their statistical associations. Interpretation of specific relationships revealed is given and implications for dynamic simulation models are discussed. Canonical correspondence analysis revealed that both microbial feeding nematodes (MF) and plant feeding nematodes (PF) appear to prefer a high level of bacteria and moisture, glomalin and organic matter in the soil. Close scrutiny, however, reveals that microbial feeding nematodes have a particularly high affinity to the sites with a high level of bacteria and organic matter, whilst plant feeding nematodes appear to be more associated with moisture and glomalin. Folsomia candida was abundant in sites with a higher pH level (pH ranged between 3.1 and 4.9), but was not abundant in sites with high ergosterol or a high bacteria, moisture, glomalin and organic matter level. However, other Collembola (mainly represented by Folsomia quadrioculata) appeared to be associated with high levels of ectomycorrhizal fungi. As F. candida is known to feed on fungal food sources, the results suggest that the relatively high local abundances of this collembolan might have caused local declines in ectomycorrhizal fungi, reflected, in turn, in the increase in pH. In addition, environmental plasticity of this species might have allowed them to expand into areas with low fungal density by utilising alternative food sources. The fact that F. candida was a dominant microarthropod in the majority of the samples collected in this research also supports this point. However, for those samples where F. candida were less abundant, overcompensatory fungal growth due to grazing by mites and other Collembola was implicated. Overall, our results suggest that both direct negative and indirect positive effects of the microarthropod community on specific fungal groups appear to take place. The differential effect of specific mesofaunal groups on other soil biota justifies their detailed representation in dynamic simulation models of soil ecosystems.

Assessing the relationship between the dry rot fungus Serpula lacrymans and selected forms of masonry

Abstract During this investigation into the relationship between the domestic dry rot fungus, Serpula lacrymans, and some non-woody building materials, it was found that S. lacrymans removed calcium, silicon and iron from sandstone, and calcium, sulphur and iron from traditional plaster. The sequestered elements were located on its hyphae, especially in the form of calcium oxalate. Degradation of the sandstone was implicit, but not obvious microscopically. In addition, S. lacrymans selectively transported iron from these building materials through its mycelial system. These findings lend further support to the theory that this wood-decaying fungus has an special dependence upon masonry in buildings.

Isolation and environmental study of ‘wild’ Serpula lacrymans and Serpula himantioides from the Himalayan forests

We report the first successful culturing and confirmation of identity (via sodium dodecyl sulphate polyacrylamide gel electrophoresis, SDS–PAGE) of Serpula lacrymans (the dry rot fungus) derived from basidiomes and mycelia growing in the ‘wild’. The fungus was found growing on well decayed coniferous wood within the Narkanda region of the Western Himalayas at between 2800 and 3100 m above sea level (a.s.l.). The ‘wild’ habitat of the fungus is described, as is the isolation of Serpula himantioides also found in these regions. Temperature, osmotic potential, initial pH and air-current influenced the average colony extension rate of ‘wild’ and a selection of building isolates on 2% malt extract agar. The ‘wild’ and building isolates behaved as two separate cohorts; the ‘wild’ isolates appeared to be less affected by extremes of temperature, whereas building isolates extended more rapidly at the moderate microenvironmental regimes.