Social odours covary with bacterial community in the anal secretions of wild meerkats.

The fermentation hypothesis for animal signalling posits that bacteria dwelling in an animal's scent glands metabolize the glands' primary products into odorous compounds used by the host to communicate with conspecifics. There is, however, little evidence of the predicted covariation between an animal's olfactory cues and its glandular bacterial communities. Using gas chromatography-mass spectrometry, we first identified the volatile compounds present in 'pure' versus 'mixed' anal-gland secretions ('paste') of adult meerkats (Suricata suricatta) living in the wild. Low-molecular-weight chemicals that likely derive from bacterial metabolism were more prominent in mixed than pure secretions. Focusing thereafter on mixed secretions, we showed that chemical composition varied by sex and was more similar between members of the same group than between members of different groups. Subsequently, using next-generation sequencing, we identified the bacterial assemblages present in meerkat paste and documented relationships between these assemblages and the host's sex, social status and group membership. Lastly, we found significant covariation between the volatile compounds and bacterial assemblages in meerkat paste, particularly in males. Together, these results are consistent with a role for bacteria in the production of sex- and group-specific scents, and with the evolution of mutualism between meerkats and their glandular microbiota.

The "secret" in secretions: methodological considerations in deciphering primate olfactory communication.

Olfactory communication in primates is gaining recognition; however, studies on the production and perception of primate scent signals are still scant. In general, there are five tasks to be accomplished when deciphering the chemical signals contained in excretions and secretions: (1) obtaining the appropriate samples; (2) extracting the target organic compounds from the biological matrix; (3) separating the extracted compounds from one another (by gas chromatography, GC or liquid chromatography, LC); (4) identifying the compounds (by mass spectrometry, MS and associated procedures); and (5) revealing biologically meaningful patterns in the data. Ultimately, because some of the compounds identified in odorants may not be relevant, associated steps in understanding signal function involve verifying the perception or biological activity of putative semiochemicals via (6) behavioral bioassays or (7) receptor response studies. This review will focus on the chemical analyses and behavioral bioassays of volatile, primate scent signals. Throughout, we highlight the potential pitfalls of working with highly complex, chemical matrices and suggest ways for minimizing problems. A recurring theme in this review is that multiple approaches and instrumentation are required to characterize the full range of information contained in the complex mixtures that typify primate or, indeed, many vertebrate olfactory cues. Only by integrating studies of signal production with those verifying signal perception will we better understand the function of olfactory communication.

Burkholdines from Burkholderia ambifaria: antifungal agents and possible virulence factors.

Burkholdines are cyclic lipopeptides with unusual antifungal potency, making them promising leads as a new class of antifungal agents. However, a recent report using knockout mutagenesis indicates that these and related compounds, such as occidiofungins, xylocandins, and cepacidines, may also be synonymous with the long-known hemolytic virulence factors found in diverse Burkholderia isolates. Because of their possible roles in causing Burkholderia infections or curing fungal infections, it is important to fully define their structures and biological activities using pure compounds. Here, we report the structures of three further burkholdines, Bk-1119, Bk-1213, and Bk-1215, which were elucidated using spectroscopic methods. The absolute configuration of this compound class was determined for the first time using a combination of spectroscopy and chemical degradation techniques. Antifungal and hemolytic activities were assessed for five pure burkholdines, representative of the structural diversity of this lipopeptide class. All of the burkholdines were potent antifungal and hemolytic agents, validating their probable role in virulence. However, one of the burkholdines (Bk-1119) exhibited a >30-fold selectivity for fungi versus sheep erythrocytes and was more than 25-fold more potent than amphotericin against some fungal strains. Therefore, burkholdines have potential to selectively target fungal infections.

Eulemur, me lemur: the evolution of scent-signal complexity in a primate clade.

Signal complexity has been linked to social complexity in vocal, but not chemical, communication. To address this gap, we examined the chemical complexity of male and female glandular secretions in eight species of Eulemur. In this diverse clade of macrosmatic primates, species differ by social or mating system and dominance structure. We applied principal component and linear discriminate analyses to data obtained by gas chromatography/mass spectrometry. Beyond the significant effects on chemical signals of gland type, sex, season and species, we found effects of social variables and phylogeny. Notably, female odours were more chemically complex in multimale-multifemale species than pair-bonded species, whereas male odours were more chemically complex in codominant species than female-dominant species. Also, the traditional sexual dimorphism, whereby male signal complexity exceeds that of females, was present in codominant species, but reversed in female-dominant species. Lastly, a positive relationship between the species' pairwise chemical distances and their pairwise phylogenetic distances supported a gradual, but relatively fast mode of signal evolution. We suggest that the comparative method can be a powerful tool in olfactory research, revealing species differences relevant to the understanding of current signal utility and evolutionary processes. In particular, social complexity in lemurs may have selected for olfactory complexity.

Burkholdines 1097 and 1229, potent antifungal peptides from Burkholderia ambifaria 2.2N.

Potent antifungal cyclic lipopeptides, burkholdines (Bk), were isolated from a culture of Burkholderia ambifaria 2.2N. Bk-1229 (1) and Bk-1097 (2) are octapeptides comprised of nonproteinogenic amino acids, including beta-hydroxytyrosine, beta-hydroxyasparagine, and a new fatty acyl amino acid. 1 and 2 are fungicidal against a panel of fungi with potencies 2-60-fold better than amphotericin B control.

FAB mass spectrometry of Au25(SR)18 nanoparticles.

The molecular ion of the nanoparticle Au 25(SCH 2CH 2Ph) 18 (A 25(SR) 18) is observed at 7394 Da in fast atom bombardment (FAB, Xe atoms) ionization mass spectrometry using a 3-nitrobenzyl alcohol matrix. A distinctive pattern of positive fragment ions is evident in the mass interval 5225-7394 Da, where peaks are seen for successive mass losses equivalent to R 2S entities. Because the Au 25(SCH 2CH 2Ph) 18 nanoparticle structure is crystallographically known to consist of a centered Au 13 icosahedral core surrounded by six Au 2(SR) 3 semirings, the R 2S loses are proposed to represent serial rearrangements and decompositions of the semiring structures. Mass losses equivalent to R 2S 2 and R 2 entities also appear at the lower end of this mass interval. The most intense spectral peak, at m/ z = 5246 Da, is assigned to the fragment Au 25S 10, from which all of the CH 2CH 2Ph organic units have been cleaved but from which no gold atoms have been lost. A different pattern of fragmentation is observed at lower masses, producing ions corresponding to serial losses of one gold atom and varied numbers of sulfur atoms, which continues down to a Au 9S 2 fragment. FAB mass spectra of the Au nanoparticle are much easier to interpret than laser desorption/ionization spectra, but they show more extensive fragmentation than do electrospray and low laser pulse intensity MALDI spectra. The loss of R 2S fragmentation in FAB is distinctive and unlike that seen in the other ionization modes. The FAB spectrum for the nanoparticle Au 25(S(CH 2) 9CH 3) 18 is also reported; its fragmentation parallels that for Au 25(SCH 2CH 2Ph) 18, implying that this nanoparticle has the same surprising stellated (staples) structure.

Nanoparticle MALDI-TOF mass spectrometry without fragmentation: Au25(SCH2CH2Ph)18 and mixed monolayer Au25(SCH2CH2Ph)(18-x)(L)(x).

Intact molecular ions of the organothiolate-protected nanoparticle Au25(SCH2CH2Ph)18, including their isotopic resolution, can be observed at 7391 Da as 1- and 1+ ions in negative and positive mode, respectively, by MALDI-TOF mass spectrometry when using a tactic of threshold laser pulse intensities and trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) as matrix. Previous MALDI-TOF studies of Au nanoparticles using other matrices have encountered extensive fragmentation of nanoparticle as well as thiolate ligands. Absence of fragmentation enables precise determination of the distribution of mixed monolayer compositions on nanoparticles prepared by ligand exchange reactions and by synthesis using thiol mixtures. Reaction conditions producing mixed monolayers containing only one or a small number of usefully functional ligands can be readily identified. At increased laser pulse intensity, the first fragmentation step(s) for the Au25(SCH 2CH2Ph)18 nanoparticle results in losses of AuL units and, in particular, loss of Au4(SCH2CH2Ph)4.

Chemical composition of scent marks in the ringtailed lemur (Lemur catta): glandular differences, seasonal variation, and individual signatures.

The apocrine and sebaceous scent glands of ringtailed lemurs (Lemur catta) appear to serve different social functions. In behavioral experiments, lemurs modulate their responses to scent marks based on the type of odorant, their own physiological state, the signaler's physiological state, and prior social experience. To examine variation in odorant chemistry relative to olfactory behavior, we used gas chromatography and mass spectrometry to analyze over 86 samples of glandular secretion collected over 2 years from 15 adult lemurs. Labial and scrotal secretions contained organic acids and esters, whereas male brachial secretions were composed almost entirely of squalene and cholesterol derivatives. Principal component and linear discriminant analyses revealed glandular, individual-specific, and seasonal variation in chemical profiles but no relationship to the signaler's social status. The chemical composition of the various secretions provides further clues about the function of the different glands: the higher molecular weight compounds in genital and brachial secretions may increase signal longevity and provide lasting information to conspecifics, consistent with a role in advertising resource ownership or reproductive state. Conversely, the lower molecular weight compounds of antebrachial secretions produce ephemeral signals used primarily in social dominance displays and require integration of multiple sensory modalities for effective signal transmission.

Increased rate of glutathione synthesis from cystine in drug-resistant MCF-7 cells.

The rate of glutathione synthesis was determined in drug-sensitive and -resistant MCF-7 cells by monitoring the rate of label uptake from [3,3'-13C(2)]-cystine using NMR spectroscopy and mass spectrometry. Compared with the wild-type human mammary adenocarcinoma cell line (MCF-7wt), the isotope incorporation rate was increased 1.6-, 2.4-, and 5.3-fold in the etoposide-resistant MCF-7 cell line (MCF-7vp), doxorubicin-resistant MCF-7 cell line (MCF-7adr), and 4-hydroperoxycyclophosphamide-resistant MCF-7 cell line (MCF-7hc), respectively. The increase in glutathione metabolism in the MCF-7hc line correlated with steady-state levels as determined by biochemical assay. In contrast, both the MCF-7vp and MCF-7adr lines showed increased metabolic synthesis of glutathione but displayed lower steady-state levels compared with the MCF-7wt line. The increased synthetic rates of all resistant lines reflected, in part, contributions from the increased activities of both gamma-glutamyltranspeptidase and gamma-glutamylcysteine synthetase. These results emphasize the importance of monitoring glutathione metabolic rates, rather than steady-state levels of enzymes or substrates, for assessing drug resistance.