Intercellular signaling plays an important role in spatially regulated developmental processes. Myxococcus xanthus C signal transmission during fruiting body formation requires motile, densely packed, well aligned cells. tThe fruiting body consists of two domains: an outer domain which has densely packed, well aligned, motile cells: and an inner domain of more loosely packed, non‐motile, sporulating cells. The two domains are characterized by different patterns of C‐dependent gene expression, which begins in the outer domain where C‐signaling is most efficient, (...) and reaches its maximum in the inner domain. These domains may be maintained by a dynamic mechanism which relies on passive transport of the sporulating cells from the outer domain, where sporulation is initiated, to the inner domain by the motile cells in the outer domain. (shrink)

M. xanthus has a complex multicellular lifestyle including swarming, predation and development. These behaviors depend on the ability of the cells to achieve directed motility across solid surfaces. M. xanthus cells have evolved two motility systems including Type‐IV pili that act as grappling hooks and a controversial engine involving mucus secretion and fixed focal adhesion sites. The necessity for cells to coordinate the motility systems and to respond rapidly to environmental cues is reflected by a complex genetic network (...) involving at least three complete sets of chemosensory systems and eukaryotic‐like signaling proteins. In this review, we discuss recent advances suggesting that motor synchronization results from spatial oscillations of motility proteins. We further propose that these dynamics are modulated by the action of multiple upstream complementary signaling systems. M. xanthus is thus an exciting emerging model system to study the intricate processes of directed cell migration. BioEssays 30:733–743, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

The outer membrane (OM) is an essential barrier that guards Gram‐negative bacteria from diverse environmental insults. Besides functioning as a chemical gatekeeper, the OM also contributes towards the strength and stiffness of cells and allows them to sustain mechanical stress. Largely influenced by studies of Escherichia coli, the OM is viewed as a rigid barrier where OM proteins and lipopolysaccharides display restricted mobility. Here the discussion is extended to other bacterial species, with a focus on Myxococcus xanthus. In (...) contrast to the rigid OM paradigm, myxobacteria possess a relatively fluid OM. It is concluded that the fluidity of the OM varies across environmental species, which is likely linked to their evolution and adaptation to specific ecological niches. Importantly, a fluid OM can endow bacteria with distinct functions for cell‐cell and cell‐environment interactions. (shrink)

For decades, myxobacteria have been spotlighted as exemplars of social “wolf‐pack” predation, communally secreting antimicrobial substances into the shared public milieu. This behavior has been described as cooperative, becoming more efficient if performed by more cells. However, laboratory evidence for cooperativity is limited and of little relevance to predation in a natural setting. In contrast, there is accumulating evidence for predatory mechanisms promoting “selfish” behavior during predation, which together with conflicting definitions of cooperativity, casts doubt on whether microbial “wolf‐pack” predation (...) really is cooperative. Here, it is hypothesized that public‐goods‐mediated predation is not cooperative, and it is argued that a holistic model of microbial predation is needed, accounting for predator and prey relatedness, social phenotypes, spatial organization, activity/specificity/transport of secreted toxins, and prey resistance mechanisms. Filling such gaps in our knowledge is vital if the evolutionary benefits of potentially costly microbial behaviors mediated by public goods are to be properly understood. (shrink)

The nm23 gene, a putative metastasis suppressor gene, was originally identified by its reduced expression in highly metastatic K‐1735 murine melanoma cell lines, as compared to related, low metastatic melanoma cell lines. Transfection of nm23 cDNA has been reported to suppress malignant progression in Drosophila and mammalian cells. Highly conserved homologues of nm23 have been found in organisms ranging from the prokaryote Myxococcus xanthus to Drosophila, where the gene is involved in normal development and differentiation. The product of (...) the nm23 gene exhibits a nucleoside diphosphate kinase activity, yet the nucleoside diphosphate kinase activity of Nm23 does not correlate with its apparent biological functions. We review recent cellular, genetic, biochemical and X‐ray crystallographic data to formulate and evaluate hypotheses concerning the molecular mechanism of nm23 action. (shrink)

Chemosensory systems are complex regulatory pathways capable of perceiving external signals and translating them into different cellular behaviors such as motility and development. In the δ-proteobacterium Myxococcus xanthus, chemosensing allows groups of cells to orient themselves and aggregate into specialized multicellular biofilms termed fruiting bodies. M. xanthus contains eight predicted CSS and 21 chemoreceptors. In this work, we systematically deleted genes encoding components of each CSS and chemoreceptors and determined their effects on M. xanthus social behaviors. (...) Then, to understand how the 21 chemoreceptors are distributed among the eight CSS, we examined their phylogenetic distribution, genomic organization and subcellular localization. We found that, in vivo, receptors belonging to the same phylogenetic group colocalize and interact with CSS components of the respective phylogenetic group. Finally, we identified a large chemosensory module formed by three interconnected CSS and multiple chemoreceptors and showed that complex behaviors such as cell group motility and biofilm formation require regulatory apparatus composed of multiple interconnected Che-like systems. © 2014 Moine et al. (shrink)

Two fragments of the Lydiaca attributed to Xanthus of Lydia preserve a curious claim that a king of Lydia was the first person to make eunuchs of women. In an attempt to make sense of these passages, it has been suggested that εὐνουχίζειν here refers not to castration, but rather to female genital cutting. If correct, this would provide our first evidence of this practice in Lydian culture or indeed anywhere in Anatolia. However, the assumption that what Xanthus (...) describes somehow related to real practices is highly questionable. Instead, we should re-contextualize this story in terms of other fifth-century representations of luxury and eunuchs and in terms of Xanthus’ own exemplary portraits of other Lydian kings. (shrink)

Diogenes Laertius (8.63-6) preserves a fascinating account of the Presocratic philosopher Empedocles' life. There, drawing on evidence from Aristotle, Xanthus, and Timaeus of Tauromenium, the biographer provides several anecdotes which are meant to demonstrate how Empedocles had, contrary to expectation, been a democratic philosopher - a paradox of itself in Ancient Greece. This article unpacks the complex web woven by Diogenes and argues that there is no good reason to assume that Empedocles was indeed a democratic philosopher, and moreover, (...) that neither Xanthus nor Aristotle thought him so. Indeed, what Diogenes actually preserves for us is the Hellenistic biographer Timaeus' critical dialectical engagement with the versions Aristotle and Xanthus, in his anachronistic bid to render Empedocles a democratic hero. (shrink)

This article examines allusions to Greek poetry in two Greek verse inscriptions carved on public monuments for Lycian dynasts of the late fifth and early fourth centuriesb.c.(CEG177, 888). Scholarship on these epigrams celebrating the rule, achievements and outstanding qualities of the dynasts Gergis (LycianKheriga) and Arbinas (Erbinna) has largely focussed on the evidence they provide for Lycian history, dynastic ideology and Lycia's relationship to Greece. Less attention has been paid to the possible significance of their long-noted echoes of Greek poetry. (...) Literary analysis of these epigrams has been sidelined, it seems, owing to a prevailing assumption that they were composed and inscribed primarily for Greeks visiting or resident in Xanthus, the Lycian ‘capital’ where they were inscribed, and so their literariness, unheard by Lycian ears, cannot add to our understanding of Lycia and Lycians. Yet, a recent observation of Peter Thonemann suggests that the appropriation and manipulation of Greek poetry is in fact central to the dynastic intent of the epigrams: to assert Lycia's non-Greek, ‘Asiatic’ identity. (shrink)

In Book 6.88–94 of the Aeneid reference is made by the Cumaean Sibyl to the fact that there will be terrible wars on the Trojans' arrival at Lavinium. The details given by the Sibyl evoke the war at Troy; there will be a Simois, a Xanthus, and a Greek camp. Moreover, there will be another Achilles in Latium and the war will again be fought over a woman. Aeneas, when he hears this, has just arrived in Italy after the (...) war at Troy and a gruelling seven-year journey. The prophecy is therefore the last thing that he wants to hear, but he responds very stoically and then proceeds to ask the Sibyl's permission to enter the Underworld . Aeneas' filial pietas is therefore stressed by his determination to meet with his father's shade in the face of forthcoming adversity. (shrink)

The phrase ἐγχέλυές τε καὶ ἰχθύες (‘eels and fish’) appears twice inIliadBook 21, in descriptions of actions involving the river Xanthus:τὸν μὲν ἄρ’ ἐγχέλυές τε καὶ ἰχθύες ἀμφεπένοντο (203)the eels and fish dealt with him [sc. Asteropaeus].τείροντ᾽ ἐγχέλυές τε καὶ ἰχθύες οἱ κατὰ δίνας (353)distressed were the eels and fish beneath the eddies.The context in which these verses appear is not that important here, as this combination of words itself raised an interpretative problem in the minds of some ancient (...) Homeric scholars: why did Homer distinguish eels and fish when eels are a kind of fish? For instance, according to Aristonicus, Aristarchus flagged both passages ‘because Homer distinguished the eels from the fish’—and Homer would not have done that, is the implication, or it is puzzling that he did so, as he must have known that eelsarea kind of fish. (shrink)

In his lengthy survey of the cosmic devastation wrought by Phaethon's disastrous chariot ride, Ovid includes two catalogues detailing the scorching of the world's mountains and rivers. Ovid enlivens these lists through his usual play with sound patterns and revels in the opportunity to adapt so many Greek names to Latin prosody; for instance the opening line of the catalogue of mountains masterfully illustrates both of these features. The lists are also brimming with playful erudition. To take but a few (...) examples: a dried-up Ida belies its standard epithet πολυπῖδαξ, ‘many-fountained’ ; the sun's heat doubles the flames of volcanic Etna ; burning Xanthus is destined to burn again ; and the famous gold-bearing sands of the Tagus are melting. These features not only ‘relieve monotony’; they warrant the catalogues’ inclusion in the category of Ovid's most entertaining. (shrink)