Department of Microbiology, Stellenbosch University, Private Bag X1, Stellenbosch, South Africa.
Microb Ecol. 2011 Oct;62(3):609-19. doi: 10.1007/s00248-011-9869-9. Epub 2011 May 18.
The yeast-like fungus Coniochaeta pulveracea was studied with regard to its novel lignocellulolytic activities and the possible effect thereof on yeasts from the woody phylloplane. An enrichment procedure was used to isolate C. pulveracea from a decaying Acacia tree, and the identity of the isolate was confirmed using morphology, as well as molecular and phylogenetic techniques. This isolate, as well as strains representing C. pulveracea from different geographical regions, were compared with regard to optimum growth temperature and enzyme activity to representatives of closely related species. These include strains of Coniochaeta boothii, Coniochaeta rhopalochaeta, and Coniochaeta subcorticalis. Plate assays for cellulase and xylanase activity indicated that all representatives of the above-mentioned species were able to produce extracellular hydrolytic enzymes and were also able to degrade birchwood toothpicks during a 50-day incubation period at 30°C. To test the ability of these fungi and their enzymes to release simple sugars from complex cellulosic substrates, filtrates obtained from liquid cultures of Coniochaeta, cultivated on carboxymethyl cellulose (CMC) as sole carbon source, were analyzed using high-performance liquid chromatography analysis. Consequently, the presence of mono- and disaccharides such as glucose and cellobiose was confirmed in these culture filtrates. Two subsequent experiments were conducted to determine whether these simple sugars released from woody material by Coniochaeta may enhance growth of phylloplane yeasts. In the first experiment, representatives of Coniochaeta were co-cultured with selected yeasts suspended in agar plates containing birchwood toothpicks, followed by examination of plates for colony formation. Results indicated that Coniochaeta growth on the toothpicks enhanced growth of nearby yeast colonies in the agar plates. In the second experiment, representatives of selected yeasts and Coniochaeta species were co-cultured on CMC and xylan-containing plates where after yeast colony formation was recorded on the plates. Saccharomyces cerevisiae strains, engineered to utilize specific wood degradation products, i.e., cellobiose or xylose, as sole carbon source were used as positive controls. While it was found that cellobiose released from CMC was assimilated by the yeasts, no evidence could be obtained that xylose released from xylan was used as carbon source by the yeasts. These ambiguous results could be ascribed to secretion of nutritious metabolic end products, other than the products of fungal xylanases.
研究了酵母样真菌康氏木霉（Coniochaeta pulveracea）的新型木质纤维素分解活性及其对木质叶片真菌的可能影响。采用富集程序从腐烂的金合欢树上分离康氏木霉，并通过形态学以及分子和系统发育技术确认分离株的身份。该分离株以及代表不同地理区域的康氏木霉菌株与密切相关物种的代表菌株进行了最佳生长温度和酶活性的比较。这些菌株包括康氏木霉（Coniochaeta boothii）、康氏木霉（Coniochaeta rhopalochaeta）和康氏木霉（Coniochaeta subcorticalis）的菌株。平板酶活性测定表明，上述所有物种的代表菌株均能产生胞外水解酶，并能在 30°C 下培养 50 天期间降解桦木牙签。为了测试这些真菌及其酶从复杂的纤维素基质中释放单糖的能力，从在羧甲基纤维素（CMC）上作为唯一碳源培养的康氏木霉液体培养物中获得的滤液使用高效液相色谱分析进行了分析。因此，在这些培养物滤液中确认了单糖和二糖（如葡萄糖和纤维二糖）的存在。进行了两项后续实验，以确定康氏木霉从木质材料中释放的这些简单糖是否可以促进叶片真菌的生长。在第一项实验中，将代表康氏木霉的菌株与悬浮在含有桦木牙签的琼脂平板中的选定酵母共培养，然后检查平板上的菌落形成情况。结果表明，牙签上的康氏木霉生长增强了琼脂平板上附近酵母菌落的生长。在第二项实验中，将选定的酵母和康氏木霉物种的代表菌株在含有 CMC 和木聚糖的平板上共培养，然后记录平板上的酵母菌落形成情况。作为阳性对照，使用经过工程改造以利用特定木质降解产物（即纤维二糖或木糖）作为唯一碳源的酿酒酵母（Saccharomyces cerevisiae）菌株。虽然发现从 CMC 释放的纤维二糖被酵母同化，但没有证据表明从木聚糖释放的木糖被酵母用作碳源。这些模棱两可的结果可能归因于除真菌木聚糖酶的营养代谢终产物之外的分泌。
