| 1. |
- Leong, Su-lin L., et al.
(författare)
-
Genome and physiology of the ascomycete filamentous fungus Xeromyces bisporus, the most xerophilic organism isolated to date
- 2015
-
Ingår i: Environmental Microbiology. - Hoboken, USA : Wiley-Blackwell. - 1462-2912 .- 1462-2920. ; 17:2, s. 496-513
-
Tidskriftsartikel (refereegranskat)abstract
- Xeromyces bisporus can grow on sugary substrates down to 0.61, an extremely low water activity. Its genome size is approximately 22Mb. Gene clusters encoding for secondary metabolites were conspicuously absent; secondary metabolites were not detected experimentally. Thus, in its dry' but nutrient-rich environment, X.bisporus appears to have relinquished abilities for combative interactions. Elements to sense/signal osmotic stress, e.g. HogA pathway, were present in X.bisporus. However, transcriptomes at optimal (approximate to 0.89) versus low a(w) (0.68) revealed differential expression of only a few stress-related genes; among these, certain (not all) steps for glycerol synthesis were upregulated. Xeromyces bisporus increased glycerol production during hypo- and hyper-osmotic stress, and much of its wet weight comprised water and rinsable solutes; leaked solutes may form a protective slime. Xeromyces bisporus and other food-borne moulds increased membrane fatty acid saturation as water activity decreased. Such modifications did not appear to be transcriptionally regulated in X.bisporus; however, genes modulating sterols, phospholipids and the cell wall were differentially expressed. Xeromyces bisporus was previously proposed to be a chaophile', preferring solutes that disorder biomolecular structures. Both X.bisporus and the closely related xerophile, Xerochrysium xerophilum, with low membrane unsaturation indices, could represent a phylogenetic cluster of chaophiles'.
|
|
| 2. |
- Leong, Su-lin L., et al.
(författare)
-
The extreme xerophilic mould Xeromyces bisporus : Growth and competition at various water activities
- 2011
-
Ingår i: International Journal of Food Microbiology. - Amsterdam, Netherlands : Elsevier. - 0168-1605 .- 1879-3460. ; 145:1, s. 57-63
-
Tidskriftsartikel (refereegranskat)abstract
- Little is known about the mould, Xeromyces bisporus, unique in its strong xerophilicity and ability to grow at water activity (a(w)) 0.62, lower than for any other known organism. The linear growth rates of one fast and one slow-growing strain of X. bisporus were assessed at 20, 25, 30 and 37 degrees C on solid agar media containing a mixture of glucose and fructose to reduce a(w) to 0.94, 0.88, 0.84, 0.80, 0.76 and 0.66. Growth rates of xerophilic species closely related to X. bisporus, viz. Chrysosporium Mops, C. xerophilum and Monascus eremophilus, were also assessed. Optimal conditions for growth of both X. bisporus strains were approx. 0.84 a(w) and 30 degrees C, despite FRR 2347 growing two- to five-fold faster than CBS 185.75. X. bisporus FRR 2347 even grew well at 0.66 a(w) (0.48 mm/day). C. Mops and C xerophilurn were more tolerant of high a(w) than X. bisporus. and could be differentiated from each other based on: the faster growth of C. xerophilum; its preference for temperatures >= 30 degrees C and a(w) >= 0.94 (c.f. <= 25 degrees C and similar to 0.88 a(w) for C Mops); and its ability to grow at 0.66 a(w), which is the lowest a(w) reported to date for this species. M. eremophilus grew slowly (max. 0.4 mm/day) even in its optimal conditions of similar to 0.88 a(w) and 25 degrees C. To investigate the competitive characteristics of X. bisporus at low a(w), both X. bisporus strains were grown in dual-culture with xerotolerant species Aspergillus flavus and Penicillium roqueforti, and xerophilic species A. penicillioides, C. Mops, C. xerophilum and Eurotium chevalieri, on glucose-fructose agar plates at 0.94, 0.84, 0.80 and 0.76 a(w) and at 25 degrees C. Growth rates and types of interactions were assessed. Excretion of inhibitory substances acting over a long-range was not observed by any species; inhibitors acting over a short-range that temporarily slowed competitors' growth or produced a protective zone around the colony were occasionally observed for A. penicillioides, C. Mops and C. xerophilum. Instead, rapid growth relative to the competitor was the most common means of dominance. The xerotolerant species. A. flavus and P. roqueforti were dominant over X. bisporus at 0.94 a(w). E. chevalieri was often dominant due to its rapid growth over the entire a(w) range. At a(w) < 0.80, X. bisporus was competitive because it grew faster than the other species examined. This supports the concept that its ideal environmental niche is sugary foods with low a(w).
|
|
| 3. |
- Pierson, D. C., et al.
(författare)
-
An automated method to monitor lake ice phenology
- 2011
-
Ingår i: Limnology and Oceanography. - : Wiley. - 1541-5856. ; 9, s. 74-83
-
Tidskriftsartikel (refereegranskat)abstract
- A simple method to automatically measure the date of ice-on, the date of ice-off, and the duration of lake ice cover is described. The presence of ice cover is detected by recording water temperature just below the ice/water interface and just above the lake bottom using moored temperature sensors. The occurrence of ice-on rapidly leads to detectible levels of inverse stratification, defined as existing when the upper sensor records a temperature at least 0.1 degrees C below that of the bottom sensor, whereas the occurrence of ice-off leads to the return of isothermal mixing. Based on data from 10 lakes over a total of 43 winter seasons, we found that the timing and duration of inverse stratification monitored by recording temperature sensors compares well with ice cover statistics based on human observation. The root mean square difference between the observer-based and temperature-based estimates was 7.1 d for ice-on, 6.4 d for ice-off, and 10.0 d for the duration of ice cover. The coefficient of determination between the two types of estimates was 0.93, 0.86, and 0.91, respectively. The availability of inexpensive self-contained temperature loggers should allow expanded monitoring of ice cover in a large and diverse array of lakes. Such monitoring is needed to improve our ability to monitor the progression of global climate change, and to improve our understanding of the relationship between climate and ice cover over a wide range of temporal and spatial scales.
|
|
| 4. |
- Tenow, Olle, et al.
(författare)
-
Geometrid outbreak waves travel across Europe
- 2013
-
Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 82:1, s. 84-95
-
Tidskriftsartikel (refereegranskat)abstract
- We show that the population ecology of the 9- to 10-year cyclic, broadleaf-defoliating winter moth (Operophtera brumata) and other early-season geometrids cannot be fully understood on a local scale unless population behaviour is known on a European scale. Qualitative and quantitative data on O. brumata outbreaks were obtained from published sources and previously unpublished material provided by authors of this article. Data cover six decades from the 1950s to the first decade of twenty-first century and most European countries, giving new information fundamental for the understanding of the population ecology of O. brumata. Analyses on epicentral, regional and continental scales show that in each decade, a wave of O. brumata outbreaks travelled across Europe. On average, the waves moved unidirectionally ESE-WNW, that is, toward the Scandes and the Atlantic. When one wave reached the Atlantic coast after 9-10 years, the next one started in East Europe to travel the same c. 3000 km distance. The average wave speed and wavelength was 330 km year-1 and 3135 km, respectively, the high speed being incongruous with sedentary geometrid populations. A mapping of the wave of the 1990s revealed that this wave travelled in a straight E-W direction. It therefore passed the Scandes diagonally first in the north on its way westward. Within the frame of the Scandes, this caused the illusion that the wave moved N-S. In analogy, outbreaks described previously as moving S-N or occurring contemporaneously along the Scandes were probably the result of continental-scale waves meeting the Scandes obliquely from the south or in parallel. In the steppe zone of eastern-most and south-east Europe, outbreaks of the winter moth did not participate in the waves. Here, broadleaved stands are small and widely separated. This makes the zone hostile to short-distance dispersal between O. brumata subpopulations and prevents synchronization within meta-populations. We hypothesize that hostile boundary models, involving reciprocal host-herbivore-enemy reactions at the transition between the steppe and the broadleaved forest zones, offer the best explanation to the origin of outbreak waves. These results have theoretical and practical implications and indicate that multidisciplinary, continentally coordinated studies are essential for an understanding of the spatio-temporal behaviour of cyclic animal populations.
|
|
| 5. |
- Vinnere Pettersson, Olga, et al.
(författare)
-
Phylogeny and intraspecific variation of the extreme xerophile, Xeromyces bisporus
- 2011
-
Ingår i: Fungal Biology. - Oxon, United Kingdom : Elsevier. - 1878-6146 .- 1878-6162. ; 115:11, s. 1100-1111
-
Tidskriftsartikel (refereegranskat)abstract
- The filamentous ascomycete Xeromyces bisporus is an extreme xerophile able to grow down to a water activity of 0.62. We have inferred the phylogenetic position of Xeromyces in relation to other xerophilic and xerotolerant fungi in the order Eurotiales. Using nrDNA and betatubulin sequences, we show that it is more closely related to the xerophilic food-borne species of the genus Chrysosporium, than to the genus Monascus. The taxonomy of X. bisporus and Monascus is discussed. Based on physiological, morphological, and phylogenetic distinctiveness, we suggest that Xeromyces should be retained as a separate genus.
|
|
