Although the gastrointestinal pathogen Campylobacter jejuni was considered asaccharolytic, >50% of sequenced isolates possess an operon for l-fucose utilization. In C. jejuni NCTC11168, this pathway confers l-fucose chemotaxis and competitive colonization advantages in the piglet diarrhea model, but the catabolic steps remain unknown. Here we solved the putative dehydrogenase structure, resembling FabG of Burkholderia multivorans. The C. jejuni enzyme, FucX, reduces l-fucose and d-arabinose in vitro and both sugars are catabolized by fuc-operon encoded enzymes. This enzyme alone confers chemotaxis to both sugars in a non-carbohydrate-utilizing C. jejuni strain. Although C. jejuni lacks fucosidases, the organism exhibits enhanced growth in vitro when co-cultured with Bacteroides vulgatus, suggesting scavenging may occur. Yet, when excess amino acids are available, C. jejuni prefers them to carbohydrates, indicating a metabolic hierarchy exists. Overall this study increases understanding of nutrient metabolism by this pathogen, and identifies interactions with other gut microbes.
Plant hormones, and especially auxins, are low molecular weight compounds highly involved in the control of plant growth and development. Auxins are also broadly used in horticulture, as part of vegetative plant propagation protocols, allowing the cloning of genotypes of interest. Over the years, large efforts have been put in the development of more sensitive and precise methods of analysis and quantification of plant hormone levels in plant tissues. Although analytical techniques have evolved, and new methods have been implemented, sample preparation is still the limiting step of auxin analysis. In this review, the current methods of auxin analysis are discussed. Sample preparation procedures, including extraction, purification and derivatization, are reviewed and compared. The different analytical techniques, ranging from chromatographic and mass spectrometry methods to immunoassays and electrokinetic methods, as well as other types of detection are also discussed. Considering that auxin analysis mirrors the evolution in analytical chemistry, the number of publications describing new and/or improved methods is always increasing and we considered appropriate to update the available information. For that reason, this article aims to review the current advances in auxin analysis, and thus only reports from the past 15 years will be covered.
Olive (Olea europaea) is one of the most important fruit species in the Mediterranean basin, where 95% of the world's olive orchards are planted, and it has become an economically valuable crop worldwide, due to an increasing interest in olive oil for human consumption. New olive orchards are being planted outside the Mediterranean, calling for an effort to identify the genotypes best adapted to the new conditions. However, some olive cultivars remain difficult to propagate, which significantly reduces the capacity to use the full genetic diversity of the species. Improving rooting ability in cuttings from recalcitrant olive cultivars has become a critical topic, which implies fundamental research on the anatomy, physiology, biochemistry and genetics of the adventitious root formation process. Besides, the existence of different rooting behaviors among olive cultivars also makes the species a candidate model plant for these studies. Olive propagation techniques evolved through time from field-or nursery-planted hardwood cuttings, to semi-hardwood cuttings in greenhouses under mist, and, more recently, to in vitro culture techniques. Nevertheless, research about adventitious root formation carried on each propagation method was mostly based on trial and error approaches. Researchers have mainly investigated different factors involved in the process of adventitious rooting by testing their effect in the rooting capacity of different cultivars, leading to a high dispersion and fragmentation of the available information. The goal of this review is to present the most relevant results achieved on adventitious root formation in olive cuttings, aiming to provide an integrated perspective of the current knowledge.
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