Spatial variations in the microbial community structure and diversity of the human foot is associated with the production of odorous volatiles.

The human foot provides an ideal environment for the colonization and growth of bacteria and subsequently is a body site associated with the liberation of odour. This study aimed to enumerate and spatially map bacterial populations' resident across the foot to understand any association with odour production. Culture-based analysis confirmed that Staphylococci were present in higher numbers than aerobic corynebacteria and Gram-positive aerobic cocci, with all species being present at much higher levels on the plantar sites compared to dorsal sites. Microbiomic analysis supported these findings demonstrating that Staphylococcus spp. were dominant across different foot sites and comprised almost the entire bacterial population on the plantar surface. The levels of volatile fatty acids, including the key foot odour compound isovaleric acid, that contribute to foot odour were significantly increased at the plantar skin site compared to the dorsal surface. The fact that isovaleric acid was not detected on the dorsal surface but was present on the plantar surface is probably attributable to the high numbers of Staphylococcus spp. residing at this site. Variations in the spatial distribution of these microbes appear to be responsible for the localized production of odour across the foot.

Functional characterisation of a SNP in the ABCC11 allele - effects on axillary skin metabolism, odour generation and associated behaviours.

BACKGROUND: A single nucleotide polymorphism (SNP), 538G→A, leading to a G180R substitution in the ABCC11 gene results in reduced concentrations of apocrine derived axillary odour precursors. OBJECTIVE: Determine the axillary odour levels in the SNP ABCC11 genotype variants and to investigate if other parameters associated with odour production are affected. METHODS: Axillary odour was assessed by subjective quantification and gas chromatography headspace analysis. Metabolite profiles, microbiome diversity and personal hygiene habits were also assessed. RESULTS: Axillary odour in the A/A homozygotes was significantly lower compared to the G/A and G/G genotypes. However, the perception-based measures still detected appreciable levels of axillary odour in the A/A subjects. Metabolomic analysis highlighted significant differences in axillary skin metabolites between A/A subjects compared to those carrying the G allele. These differences resulted in A/A subjects lacking specific volatile odourants in the axillary headspace, but all genotypes produced odoriferous short chain fatty acids. Microbiomic analysis revealed differences in the relative abundance of key bacterial genera associated with odour generation between the different genotypes. Deodorant usage indicated a high level of self awareness of axillary odour levels with A/A individuals less likely to adopt personal hygiene habits designed to eradicate/mask its presence. CONCLUSIONS: The SNP in the ABCC11 gene results in lower levels of axillary odour in the A/A homozygotes compared to those carrying the G allele, but A/A subjects still produce noticeable amounts of axillary odour. Differences in axillary skin metabolites, bacterial genera and personal hygiene behaviours also appear to be influenced by this SNP.

The secretory clear cell of the eccrine sweat gland as the probable source of excess sweat production in hyperhidrosis.

Primary hyperhidrosis is characterized by excessive sweating in palmar, plantar and axillary body regions. Gland hypertrophy and the existence of a third type of sweat gland, the apoeccrine gland, with high fluid transporting capabilities have been suggested as possible causes. This study investigated whether sweat glands were hypertrophied in axillary hyperhidrotic patients and if mechanisms associated with fluid transport were found in all types of axillary sweat glands. The occurrence of apoeccrine sweat glands was also investigated. Axillary skin biopsies from control and hyperhidrosis patients were examined using immunohistochemistry, image analysis and immunofluorescence microscopy. Results showed that glands were not hypertrophied and that only the clear cells in the eccrine glands expressed proteins associated with fluid transport. There was no evidence of the presence of apoeccrine glands in the tissues investigated. Preliminary findings suggest the eccrine gland secretory clear cell as the main source of fluid transport in hyperhidrosis.

Co-expression of N-terminal truncated 3-hydroxy-3-methylglutaryl CoA reductase and C24-sterol methyltransferase type 1 in transgenic tobacco enhances carbon flux towards end-product sterols.

The enzymes 3-hydroxy-3-methylglutaryl CoA reductase (HMGR) and C24-sterol methyltransferase type 1 (SMT1) have been proposed to be key steps regulating carbon flux through the sterol biosynthesis pathway. To further examine this hypothesis, we co-expressed the catalytic domain of Hevea brasiliensis HMGR (tHMGR) and Nicotiana tabacum SMT1 in tobacco, under control of both constitutive and seed-specific promoters, resulting in increased accumulation of total sterol in seed tissue by 2.5- and 2.1-fold, respectively. This enhancement is greater than when tHMGR and SMT1 were expressed singularly where, for example, seed-specific expression enhanced total sterols by 1.6-fold. Significantly, the relative level of 4-desmethyl sterols (end-product sterols) was higher in seed co-expressing tHMGR and SMT1 from seed-specific promoters (79% of total sterols) than when co-expressed from constitutive promoters (59% of total sterols) and similar to wild-type seed (80% of total sterols). These results demonstrate that HMGR and SMT1 work in concert to control carbon flux into end-product sterols and that the sterol composition can be controlled by the temporal activity of the promoters driving transgene expression. In addition, constitutive expression of the transgenes resulted in elevated accumulation of substrates for C4-demethylation reactions, which indicates that one or several enzymes catalysing such reactions limit carbon flow to end-product sterols, at least in a physiological situation when the carbon flow is upregulated.

Co-ordinate regulation of sterol biosynthesis enzyme activity during accumulation of sterols in developing rape and tobacco seed.

The activities of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, sterol methyl transferase 1 and sterol acyltransferase, key enzymes involved in phytosterol biosynthesis were shown to be co-ordinately regulated during oilseed rape ( Brassica napus L.) and tobacco ( Nicotiana tabacum L.) seed development. In both plants, enzyme activities were low during the initial stages of seed development, increasing towards mid-maturation where they remained stable for a time, before declining rapidly as the oilseeds reached maturity. During seed development, the level of total sterols increased 12-fold in tobacco and 9-fold in rape, primarily due to an increase in steryl ester production. In both seed tissues, stages of maximum enzyme activity coincided with periods of high rates of sterol production, indicating developmental regulation of the enzymes to be responsible for the increases in the sterol content observed during seed development. Consistent with previous studies the data presented suggest that sterol biosynthesis is regulated by two key steps, although there may be others. The first is the regulation of carbon flux into the isoprenoid pathway to cycloartenol. The second is the flux from cycloartenol to Delta(5)-end-product sterols. The implications of the results in terms of enhancing seed sterol levels by genetic modification are also discussed.

Enhancement of seed phytosterol levels by expression of an N-terminal truncated Hevea brasiliensis (rubber tree) 3-hydroxy-3-methylglutaryl-CoA reductase.

Dietary intake of phytosterols (plant sterols) has been shown to be effective in reducing blood cholesterol levels, thereby reducing the risk of cardiovascular disease. Phytosterols are most commonly sourced from vegetable oils, where they are present as minor components. We report here the generation of transgenic tobacco seeds substantially enhanced in phytosterol content by the expression of a modified form of one of the key sterol biosynthetic enzymes, 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR). The constitutive expression of an N-terminal truncated Hevea brasiliensis HMGR (t-HMGR), lacking the membrane binding domain, enhanced seed HMGR activities by 11-fold, leading to increases in total seed sterol of 2.4-fold. Seed-specific expression of t-HMGR enhanced total seed sterol levels by 3.2-fold, to 1.36% dry weight or 3.25% of oil. 4-desmethylsterols were increased by 2.2-fold, whilst certain sterol biosynthetic intermediates, in particular cycloartenol and 24-ethylidene lophenol, also accumulated. The additional sterol in seed tissue was present in the form of fatty acid esters. Constitutive expression of t-HMGR increased leaf phytosterol sterol levels by 10-fold, representing 1.8% dry weight, and the sterol was sequestered, in acyl ester form, as cytoplasmic 'oil droplets'. These studies establish HMGR as a key enzyme controlling overall flux into the sterol biosynthesis pathway in seed tissue, but the accumulation of certain intermediates suggests additional slow steps in the pathway. The expression of an N-truncated HMGR activity has generated novel phytosterol-enriched raw materials that may provide the basis of new sourcing opportunities for this important class of cholesterol-lowering actives.

Sterol C-24 methyltransferase type 1 controls the flux of carbon into sterol biosynthesis in tobacco seed.

The first committed step in the conversion of cycloartenol into Delta(5) C24-alkyl sterols in plants is catalyzed by an S-adenosyl-methionine-dependent sterol-C24-methyltransferase type 1 (SMT1). We report the consequences of overexpressing SMT1 in tobacco (Nicotiana tabacum), under control of either the constitutive carnation etched ring virus promoter or the seed-specific Brassica napus acyl-carrier protein promoter, on sterol biosynthesis in seed tissue. Overexpression of SMT1 with either promoter increased the amount of total sterols in seed tissue by up to 44%. The sterol composition was also perturbed with levels of sitosterol increased by up to 50% and levels of isofucosterol and campesterol increased by up to 80%, whereas levels of cycloartenol and cholesterol were decreased by up to 53% and 34%, respectively. Concomitant with the enhanced SMT1 activity was an increase in endogenous 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, from which one can speculate that reduced levels of cycloartenol feed back to up-regulate 3-hydroxy-3-methylglutaryl coenzyme A reductase activity and thereby control the carbon flux into sterol biosynthesis. This potential regulatory role of SMT1 in seed sterol biosynthesis is discussed.