Deciphering unusual uncultured magnetotactic multicellular prokaryotes through genomics.

Candidatus Magnetoglobus multicellularis (Ca. M. multicellularis) is a member of a group of uncultured magnetotactic prokaryotes that possesses a unique multicellular morphology. To better understand this organism's physiology, we used a genomic approach through pyrosequencing. Genomic data analysis corroborates previous structural studies and reveals the proteins that are likely involved in multicellular morphogenesis of this microorganism. Interestingly, some detected protein sequences that might be involved in cell adhesion are homologues to phylogenetically unrelated filamentous multicellular bacteria proteins, suggesting their contribution in the early development of multicellular organization in Bacteria. Genes related to the behavior of Ca. M. multicellularis (chemo-, photo- and magnetotaxis) and its metabolic capabilities were analyzed. On the basis of the genomic-physiologic information, enrichment media were tested. One medium supported chemoorganoheterotrophic growth of Ca. M. multicellularis and allowed the microorganisms to maintain their multicellular morphology and cell cycle, confirming for the first time that the entire life cycle of the MMP occurs in a multicellular form. Because Ca. M. multicellularis has a unique multicellular life style, its cultivation is an important achievement for further studies regarding the multicellular evolution in prokaryotes.

The role of historical barriers in the diversification processes in open vegetation formations during the Miocene/Pliocene using an ancient rodent lineage as a model.

The Neotropics harbors a high diversity of species and several hypotheses have been proposed to account for this pattern. However, while species of forested domains are frequently studied, less is known of species from open vegetation formations occupying, altogether, a larger area than the Amazon Forest. Here we evaluate the role of historical barriers and the riverine hypothesis in the speciation patterns of small mammals by analyzing an ancient rodent lineage (Thrichomys, Hystricomorpha). Phylogenetic and biogeographic analyses were carried out with mitochondrial and nuclear DNA markers to analyze the evolutionary relationships between Thrichomys lineages occurring in dry domains along both banks of the Rio São Francisco. This river is one of the longest of South America whose course and water flow have been modified by inland tectonic activities and climate changes. Molecular data showed a higher number of lineages than previously described. The T. inermis species complex with 2n = 26, FN = 48 was observed in both banks of the river showing a paraphyletic arrangement, suggesting that river crossing had occurred, from east to west. A similar pattern was also observed for the T. apereoides complex. Thrichomys speciation occurred in Late Miocene when the river followed a different course. The current geographic distribution of Thrichomys species and their phylogenetic relationships suggested the existence of frequent past connections between both banks in the middle section of the Rio São Francisco. The extensive palaeodune region found in this area has been identified as a centre of endemism of several vertebrate species and is likely to be a center of Thrichomys diversification.

Biogeographic determinants of genetic diversification in the mouse opossum Gracilinanus agilis (Didelphimorphia: Didelphidae).

The genetic variation of Brazilian populations of the mouse opossum Gracilinanus agilis was analyzed on the basis of the mitochondrial Cytochrome b gene (mt-Cytb) and the exon 28 of the nuclear Von Willenbrand factor (e28-vWF). The radiation of Gracilinanus was dated at 4.80 Ma, with the appearance of G. agilis around 1.93 Ma. Gracilinanus aceramarcae appeared as the first offshoot of the genus, followed by Gracilinanus emiliae and Gracilinanus microtarsus, which composed a sister clade of G. agilis. Phylogeographic analyses and genetic distance estimates indicate G. agilis as a single species, with haplotypes grouping in three well-supported clades, one from midwestern Brazil, a second one from northeastern Brazil, and a third one from eastern Brazil. Phylogeographic patterns in G. agilis were interpreted in search for congruence between genetic breaks and historic geomorphologic events documented for the region stretching northeastern to central-western of the Brazilian shield. The Rio São Francisco and the Serra Geral de Goiás were found to represent relevant geographic barriers to gene flow for G. agilis populations as well as for populations of several other widespread taxa.

Common ancestry of iron oxide- and iron-sulfide-based biomineralization in magnetotactic bacteria.

Magnetosomes are prokaryotic organelles produced by magnetotactic bacteria that consist of nanometer-sized magnetite (Fe(3)O(4)) or/and greigite (Fe(3)S(4)) magnetic crystals enveloped by a lipid bilayer membrane. In magnetite-producing magnetotactic bacteria, proteins present in the magnetosome membrane modulate biomineralization of the magnetite crystal. In these microorganisms, genes that encode for magnetosome membrane proteins as well as genes involved in the construction of the magnetite magnetosome chain, the mam and mms genes, are organized within a genomic island. However, partially because there are presently no greigite-producing magnetotactic bacteria in pure culture, little is known regarding the greigite biomineralization process in these organisms including whether similar genes are involved in the process. Here using culture-independent techniques, we now show that mam genes involved in the production of magnetite magnetosomes are also present in greigite-producing magnetotactic bacteria. This finding suggest that the biomineralization of magnetite and greigite did not have evolve independently (that is, magnetotaxis is polyphyletic) as once suggested. Instead, results presented here are consistent with a model in which the ability to biomineralize magnetosomes and the possession of the mam genes was acquired by bacteria from a common ancestor, that is, the magnetotactic trait is monophyletic.

Population genetic studies of Alouatta caraya (Alouattinae, Primates): inferences on geographic distribution and ecology.

Cytochrome b DNA sequence data (ca. 1,140 bp) of 44 Alouatta caraya, including 42 specimens from three localities of Brazil and two from Bolivia, were used for phylogenetic reconstructions and population studies. Seventeen haplotypes were identified, eight of which were present in more than one individual. Seven of these eight haplotypes were shared by individuals from a same locality and one by individuals from two localities. We found 26 variable sites along the entire gene, consisting of 18 transitions and eight transversions; most replacements occurring at the third codon position (65.39%) in contrast to first and second positions (26.92 and 7.69%, respectively). In the sample collected at Chapada dos Guimarães (Brazil), nucleotide and haplotype diversity estimates were pi=0.002325 and h=0.8772, respectively. Maximum parsimony analysis grouped all haplotypes in two clades, separating Bolivian haplotypes from Brazilian haplotypes, the grouping of which did not show a straightforward correspondence with geographic distribution. Median-joining and TCS network pointed to haplotypes 11 or 12 as the most likely ancestral ones. Mismatch distribution and the goodness-of-fit test (SSD estimate=0.0027; P=0.6999) indicated that the population from Chapada dos Guimarães experienced a demographic expansion, in agreement with the median-joining star-like pattern, although this finding could not be confirmed by Fu's F(s) test.

The lowest diploid number (2n = 16) yet found in any primate: Callicebus lugens (Humboldt, 1811).

Morphologic, molecular and karyologic analyses of Callicebus lugens (Humboldt, 1811) of known geographic origin supported the proposition that this is a valid species. Morphologic and morphometric analyses showed evident differences between C. lugens and two other related taxa of the same group (Callicebus purinus and Callicebus torquatus). Cytochrome b DNA analyses (maximum parsimony, neighbour joining and maximum likelihood) were congruent in showing a strong association between C. lugens and Callicebus sp. of the torquatus group in one branch and a sister branch further divided into two clades: one with species of the personatus group and another, with species of the moloch group. Karyotypic analysis showed that C. lugens has the lowest diploid chromosome number of the primate order (2n = 16). Comparisons with other congeneric species clearly supported the proposition that C. lugens is karyotypically similar to others of the torquatus group.