Mitochondria and the culture of the Borg

As endosymbionts, the mitochondria are unique among organelles. This review provides insights into mitochondrial behavior and introduces the idea of a unified collective, an interconnected reticulum reminiscent of the Borg, a fictional humanoid species from the Star Trek television series whereby decisions are made within their network (or “hive”), linked to signaling cascades that coordinate the cross‐talk between mitochondrial and cellular processes (“subspace domain”). Similarly, mitochondrial dynamics are determined by two distinct processes, namely the local regulation of fission/fusion and the global control of their behavior through cellular signaling pathways. Indeed, decisions within the hive provide each mitochondrial unit with autonomous control of their own degradation, whereby mitochondrial fusion is inactivated and they become substrates for autophagy. Decisions within the subspace domain couple signaling pathways involved in the functional integration of mitochondria with complex cellular transitions, including developmental cues, mitosis, and apoptosis.     

Influence of the inoculation time of high sugar content must on the formation of wine aroma

The addition of inocula of a commercially available strain of Saccharomyces cerevisiae to musts with a high initial sugar content at various fermentation stages induces variable changes in the different components of the volatile fraction of wine and, potentially, its sensory properties as well. Inoculation alters the concentration ratio between the 2,3-butanediol isomers and causes a decrease in acetates and ethyl ester content. We propose an analytical ratio to evaluate the aromatic quality of the wine.     

Infraciliature and morphogenesis in three rumen Diplodinium ciliates, Diplodinium polygonale, Diplodinium leche, and Diplodinium nanum, observed by light microscopy

Infraciliature and morphogenesis of three rumen ophryoscolecid ciliates, Diplodinium polygonale Dogiel, 1925, Diplodinium leche Imai et al., 1992, and Diplodinium nanum Imai, 1988, are described from pyridinated silver carbonate-impregnated specimens. These three species have two polybrachykineties in the buccal area and a polybrachykinety in the dorsal ciliary zone. The vestibular polybrachykinety (VP) of D. polygonale and D. leche arises from the dorsal extremity of the adoral polybrachykinety (AP) as in Entodinium species, extending toward the left in D. polygonale and toward the left posterior in D. leche. The VP of D. nanum arises from the inner side of the AP, separate from its dorsal extremity, as in other Diplodinium species and extends toward the left posterior. These series of the polybrachykinety arrangements in D. polygonale, D. leche, and D. nanum can be regarded as transitional forms in the evolution of an Entodinium-like ancestor to Diplodinium. Morphogenesis of these three Diplodinium species is not different from that of other Diplodinium species.     

New perspectives on mitochondrial morphology in cell function

Mitochondria are a node of integration for intracellular signaling pathways and their morphology changes seem to be tightly associated with their function. New data show that morphology is one of the parameters involved in mitochondria's choice between promoting cell death and protecting cells against general metabolic jeopardy.     

Dynein participates in chromosome segregation in fission yeast

Background information. In eukaryotic cells, proper formation of the spindle is necessary for successful cell division. For faithful segregation of sister chromatids, each sister kinetochore must attach to microtubules that extend to opposite poles (chromosome bi‐orientation). At the metaphase—anaphase transition, cohesion between sister chromatids is removed, and each sister chromatid is pulled to opposite poles of the cell by microtubule‐dependent forces. Results. We have studied the role of the minus‐end‐directed motor protein dynein by analysing kinetochore dynamics in fission yeast cells deleted for the dynein heavy chain (Dhc1) or the light chain (Dlc1). In these mutants, we found an increased frequency of cells showing defects in chromosome segregation, which leads to the appearance of lagging chromosomes and an increased rate of chromosome loss. By following simultaneously kinetochore dynamics and localization of the checkpoint protein Mad2, we provide evidence that dynein function is not necessary for spindle‐assembly checkpoint inactivation. Instead, we have demonstrated that loss of dynein function alters chromosome segregation and activates the Mad2‐dependent spindle‐assembly checkpoint. Conclusions. These results show an unexpected role for dynein in the control of chromosome segregation in fission yeast, most probably operating during the process of bi‐orientation during early mitosis.     

A basidiomycetous yeast, Pseudozyma crassa, produces novel diastereomers of conventional mannosylerythritol lipids as glycolipid biosurfactants

Mannosylerythritol lipids (MELs) are glycolipid biosurfactants produced by the yeast strains of the genus Pseudozyma. These compounds show not only excellent surface-active properties, but also versatile biochemical actions. During a survey of new MEL producers, we found that a basidiomycetous yeast, Pseudozyma crassa, extracellularly produces three glycolipids. When glucose and oleic acid were used as the carbon source, the total amount of glycolipids reached approximately 4.6 g/L in the culture medium. The structures of these glycolipids were similar to those of well-known MEL-A, -B, and -C, respectively. Very interestingly, in all the present glycolipids, the configuration of the erythritol moiety was entirely opposite to that of conventional MELs. The present glycolipids were identified to have the carbohydrate structure of 4-O-β-d-mannopyranosyl-(2R,3S)-erythritol, stereochemically different from 4-O-β-d-mannopyranosyl-(2S,3R)-erythritol of conventional MELs. Furthermore, these new glycolipids possessed both short-chain acids (C₂ or C₄) and long-chain acids (C₁₄, C₁₆, or C₁₈) on the mannose moiety. The major component of the present glycolipids clearly showed different interfacial and biological properties, compared to conventional MELs comprising two medium-chain acids on the mannose moiety. Accordingly, the novel MEL diastereomers produced by P. crassa should provide us with different glycolipid functions, and facilitate a broad range of applications of MELs.     

我国各类基物上的酵母菌分布及其尿素酶活性

本文讨论了2300株由我国各地分离到的酵母菌和类酵母菌与各类基物的关系。共述及23属,占Lodder(1970)系统的半数以上。在十几类基物中酵母菌的分布各有不同,叶子上有大量掷孢酵母,果实上比其它基物更能获得克勒克酵母属(Kloeckera),在咸腌食品中相对地有较多耐高渗透压的酵母如球拟酵母属(Torulopsis)与德巴利酵母属(Debaryomyces)。对部分属的定种工作也已进行,说明某些属的种在我国均有发现而且为数不少。此外还研究了600余株代表各类酵母的尿素酶活性,结果说明担子菌酵母或系统上接近担子菌的酵母都有尿素酶活性,而子囊菌酵母则无。根据作者的观察子囊菌酵母中裂殖酵母属(Schizosaccharomyces)则常常例外地有尿素酶反应,且常有辅酶Q_(10),从而可见裂殖酵母属有其特有的生物学特性,在系统上很可能与其它子囊菌酵母不同。对属于不完全菌的无孢子酵母也进行了尿素酶活性测定,结果表明它们部分与子囊菌有关,部分与担子菌有关。     

工业酵母抗逆机理研究进展

工业酵母利用木质纤维素等生物质资源发酵生产醇、酮、醛、酸等各种化合物,是解决人类面临的不可再生资源和能源危机的重要途径,这激发了人们对木质纤维素水解液为原料和环保节能型浓醪发酵技术的极度关注。然而高浓度底物、产物、渗透压、木质纤维素水解液中抑制性物质、发酵过程温度的提高均会抑制微生物生长代谢及发酵性能,这是发酵行业"瓶颈"问题。本文简述了渗透压、温度及抑制性物质对酵母细胞生长的危害,并从胞内稳态平衡、分子水平等方面着重叙述工业酵母对渗透压、温度及抑制性物质的抗逆机制研究进展。     

Ecology of Microbial Saprophytes and Pathogens in Tissue Culture and Field-Grown Plants: Reasons for Contamination Problems In Vitro

This review compares published surveys of microbial populations in plant tissue and cell cultures with the microbial saprophytes and pathogens found on field grown plants and microbial populations in the laboratory environment. From this comparison and the measured reduction in contamination after improvements in working practices in the laboratory, conclusions can be drawn about the importance of the explant and the laboratory as sources of contamination.

Mechanisms of pathogenicity in vitro are described to explain why bacteria, fungi, and yeasts that are not pathogenic to plants in the field become pathogens in plant tissue cultures. Conversely, plant metabolism and its effect on the tissue culture environment are described to explain why prokaryotes, viruses, and viroids that cause disease in the field can stay latent in vitro.

Detection methods for latent contaminants in plant tissue cultures are summarized, and the strategies and methods for prevention or treatment of contamination are discussed.