Modelling the effect of temperature, water activity and pH on the growth of Serpula lacrymans

Aims: To predict the risk factors for building infestation by Serpula lacrymans, which is one of the most destructive fungi causing timber decay in buildings. Methods and Results: The growth rate was assessed on malt extract agar media at temperatures between 1·5 and 45°C, at water activity (a_w) over the range of 0·800–0·993 and at pH ranges from 1·5 to 11·0. The radial growth rate (μ) and the lag phase (λ) were estimated from the radial growth kinetics via the plots radius vs time. These parameters were then modelled as a function of the environmental factors tested. Models derived from the cardinal model (CM) were used to fit the experimental data and allowed an estimation of the optimal and limit values for fungal growth. Optimal growth rate occurred at 20°C, at high a_w level (0·993) and at a pH range between 4·0 and 6·0. The strain effect on the temperature parameters was further evaluated using 14 strains of S. lacrymans. The robustness of the temperature model was validated on data sets measured in two different wood‐based media (Quercus robur L. and Picea abies). Conclusions: The two‐step procedure of exponential model with latency followed by the CM with inflection gives reliable predictions for the growth conditions of a filamentous fungus in our study. The procedure was validated for the study of abiotic factors on the growth rate of S. lacrymans. Significance and Impact of the Study: This work describes the usefulness of evaluating the effect of physico‐chemical factors on fungal growth in predictive building mycology. Consequently, the developed mathematical models for predicting fungal growth on a macroscopic scale can be used as a tool for risk assessment of timber decay in buildings.     

Isolation and characterization of 15 polymorphic microsatellite markers for the devastating dry rot fungus,Serpula lacrymans

Fifteen polymorphic microsatellite markers were developed from microsatellite‐enriched DNA libraries of the devastating dry rot fungus, Serpula lacrymans. The loci exhibited two to four alleles per locus and the expected heterozygosity ranged from 0.13 to 0.47. The codominant markers, described here for this fungus, will permit further studies in population genetics and phylogeography of this economically highly important species.     

The worm re-turns: hiding behavior of a tube-dwelling marine polychaete, Serpula vermicularis

The polychaete worm Serpula vermicularis (Serpulidae) filterfeeds at the mouth of its calcareous tube, but retreats intothe tube when startled by mechanical stimuli likely to be associatedwith predators. While in its tube, a worm is safe but cannotfeed. Thus, hiding has a lost-opportunity cost. We show thatthis cost can be substantial, given that food in the naturalhabitat appears in pulses, and good feeding conditions may notlast long or recur frequently. We expect that a worm's hidingtime will be sensitive to the lost-opportunity cost, and wepresent data from a series of experiments that support thisprediction. The worms seem able to track relatively short-termchanges in food availability, and some evidence suggests thatthey assess food availability on a relative basis, comparingcurrent feeding conditions to those recently experienced. Hidingand other types of cryptic behavior are common antipredatortactics, and animals may commonly adjust the durations of suchbehaviors to current benefits and costs (including lost opportunity),as they perceive them     

中国干腐菌属的研究

中国干腐菌属共有3种,根据中国的材料对每种的担孢子进行测量和统计,并给出了该属种类的检索表,相似干腐菌为中国一新记录种,对该种进行了详细描述和显微绘图。该种的主要特征是担子果有菌盖,担孢子近球形,生长在竹子上。伏果干腐菌在欧洲经常木制房屋腐朽,但该菌在中国所引起的问题没有欧洲严重。     

RAPID ASSEMBLY OF A WOUND PLUG: STAGE ONE OF A TWO‐STAGE WOUND REPAIR MECHANISM IN THE GIANT UNICELLULAR CHLOROPHYTE DASYCLADUS VERMICULARIS (CHLOROPHYCEAE)1

Upon injury, selected coenocytic algae are capable of forming temporary wound plugs to prevent detrimental cytoplasmic loss. Wound plugs of Dasycladus vermicularis ([Scropoli] Krasser) were harvested 5 min post‐injury and dried. The plug material contained 94% water and can be considered a hydrogel. The gel plug extended several millimeters from the cut end and filled the space inside the cell wall, which resulted from cytoplasmic retraction. Total organic carbon included 55% sugars, 5%–15% protein, and 0.18% lipids. The major sugars were glucose, galactose, mannose, and galacturonic acid. Fluorescein isothiocyanate‐lectins specific for these sugars were localized around the plug matrix. Sulfur content calculated as sulfate corresponded to 17% of the carbohydrate by weight, and sulfated material was detected in plugs by Alcian Blue staining. Formation of the initial plug occurred within 1 min of injury and was not significantly perturbed by the addition of ionic, antioxidant, or chelating agents to the seawater medium. However, addition of exogenous d (+)‐galactose and d (+)‐glucose prevented formation of the nascent gel plug. Wound plugs that were allowed to form from 10 min up until 24 h post‐injury were isolated and incubated with selected biochemical probes to identify the biochemical processes involved in plug formation. The operative strategy in Dasycladus to prevent “cytoplasmic hemorrhage” required availability of sequestered carbohydrate and lectin precursor components throughout the thallus for plug assembly. Once the initial assembly had commenced, additional biochemical interactions were initiated (as a function of time) to promote structural integrity.     

EVIDENCE OF A LATENT OXIDATIVE BURST IN RELATION TO WOUND REPAIR IN THE GIANT UNICELLULAR CHLOROPHYTE DASYCLADUS VERMICULARIS1

We investigated the kinetics and composition of the second phase of the wound repair process of Dasycladus vermicularis ([Scropoli] Krasser) using fluorescent probes, chromatography, UV spectroscopy, and histochemistry. Our new evidence supports the hypothesis that the second phase of wound repair (initiated at approximately 35–45 min postinjury) is based on the activation of an oxidative burst that produces micromolar H₂O₂ levels. These results provide evidence of peroxidase activity at the wound site, real‐time measurements of an oxidative burst, and catechol localization in wound plugs. Strong evidence is presented indicating that the biochemical machinery exists for oxidative cross‐linking to ensue in the wound‐healing process of D. vermicularis.     

Molecular phylogenetics suggest a North American link between the anthropogenic dry rot fungus Serpula lacrymans and its wild relative S. himantioides

The dry rot fungus Serpula lacrymans causes damages in wooden buildings and constructions in temperate regions worldwide. In this study, the global phylogeography of S. lacrymans and its wild relative S. himantioides has been investigated to clarify genealogical relationships and determine the origin and spread of the building strains. Internal transcribed spacer (ITS) nrDNA and parts of the beta-tubulin (tub) and the translation elongation factor (efa) 1a genes were sequenced, and phylogenetic relationships inferred. Some analyses suggest that S. lacrymans may have originated from an ancient S. himantioides lineage, but most results support that S. lacrymans and S. himantioides are monophyletic sister species. Phylogenetic analysis of the ITS data revealed two subgroups within S. lacrymans corresponding to two earlier described varieties; one group occurring frequently in houses worldwide ('Domesticus'), and one group represented by individuals from forests in Northern California ('Shastensis'). A few collections from nature were included in the Domesticus group as well, among other specimens from two newly discovered localities in Far East Russia and Siberia. In the Domesticus group little sequence variation occurs, suggesting a recent worldwide dispersal, possibly linked to human activity. Phylogenetic analyses indicate that the Domesticus group may have originated from an ancient lineage related closely to the Shastensis group. A remarkable shift in morphology and habitat preferences has occurred during the evolution of the Domesticus lineage, linked to the transition from nature to human-made habitats.     

Characterization of the Bacillus subtilis CwbA protein which stimulates cell wall lytic amidases

The Bacillus subtilis cell wall binding protein, CwbA, stimulated the cell wall lytic activities of the B. subtilis and B. licheniformis autolysins (CwlA and CwlM, respectively) in addition to that of the major B. subtilis autolysin (CwlB). Even though the substrate for the enzyme reaction was changed from B. subtilis cell wall containing a teichoic acid to Micrococcus luteus cell wall containing a teichuronic acid, the stimulatory effect of CwbA on CwlA activity was observed.     

雪茶化学成分研究

由管枝衣科地茶属植物雪茶（Thamnolia vermicularis)丙酮提取物中分离得到10个成分,通过波谱分析及与已知品对照等方法,最终确定其中的9个化合物分别为:Thamnolin(1),鳞片衣酸（2）,坝巴酸（3）,羊角衣酸（4）,3β－羟基－5α,8α－桥二氧麦角甾－6,22－二烯（5）,3β－羟基－5α,8α－桥二氧麦角甾－6,9,22－三烯（6）,麦角甾烷－7,22－二烯－3－醇（7）,麦角甾烷－5,8,22－三烯－3－醇（8）,亚油酸(9)。其中,化合物1为新化合物,化合物3和6－9系首次由该种植物中分离得到。研究结果初步明确了云南中甸地区产雪茶为主要含有坝巴酸（3）和羊角衣酸（4）等酚性成分,而非主含地茶酸等酚性成分的植物品种类型,这为合理开发利用当地植物资源提供了科学依据。     

Two invasive populations of the dry rot fungus Serpula lacrymans show divergent population genetic structures

The dry rot fungus Serpula lacrymans is a devastating basidiomycete occurring in wooden constructions in temperate regions worldwide. In this study, we compare the genetic structures of two invasive populations from Europe and Japan. Microsatellite data from 14 loci and DNA sequences from four loci demonstrated that the two populations were highly differentiated. Significant isolation by distance effect was observed in Europe and Japan. Higher genetic variation was observed within the Japanese population than within the European population, corresponding with the observed higher richness of vegetative compatibility types in Japan, indicating that there has been a higher level of gene flow from the Asian source populations to Japan than to Europe. The European population is genetically more homogenous with only six detected vegetative compatibility types. Various tests indicate that both the European and the Japanese populations have gone through population bottlenecks prior to population expansion. No identical multi‐locus genotypes were observed within Japan and very few within Europe, indicating limited clonal dispersal. Deviations from Hardy Weinberg expectations were observed both in Europe and Japan and heterozygote excess were observed at several loci, especially in Europe. Possible explanations for this pattern are discussed.