Intracellular inclusions of uncultured magnetotactic bacteria

Magnetotactic bacteria produce magnetic crystals in organelles called magnetosomes. The bacterial cells may also have phosphorus-containing granules, sulfur globules, or polyhydroxyalkanoate inclusions. In the present study, the ultrastructure and elemental composition of intracellular inclusions from uncultured magnetotactic bacteria collected in a marine environment are described. Magnetosomes contained mainly defect-free, single magnetite crystals with prismatic morphologies. Two types of phosphorus-containing granules were found in magnetotactic cocci. The most common consisted of phosphorus-rich granules containing P, O, and Mg; and sometimes also C, Na, Al, K, Ca, Mn, Fe, Zn, and small amounts of S and Cl were also found. In phosphorus-sulfur-iron granules, P, O, S, Na, Mg, Ca, Fe, and frequently Cl, K, and Zn, were detected. Most cells had two phosphorus-rich granules, which were very similar in elemental composition. In rod-shaped bacteria, these granules were positioned at a specific location in the cell, suggesting a high level of intracellular organization. Polyhydroxyalkanoate granules and sulfur globules were less commonly seen in the cells and had no fixed number or specific location. The presence and composition of these intracellular structures provide clues regarding the physiology of the bacteria that harbor them and the characteristics of the microenvironments where they thrive. [Int Microbiol 2005; 8(2):111-117

Cell viability in magnetotactic multicellular prokaryotes

A magnetotactic multicellular prokaryote (MMP) is an assembly of bacterial cells organized side by side in a hollow sphere in which each cell faces both the external environment and an internal acellular compartment in the center of the multicellular organism. MMPs swim as a unit propelled by the coordinated beating of the many flagella on the external surface of each cell. At every stage of its life cycle, MMPs are multicellular. Initially, a spherical MMP grows by enlarging the size of each of its cells, which then divide. Later, the cells separate into two identical spheres. Swimming individual cells of MMPs have never been observed. Here we have used fluorescent dyes and electron microscopy to study the viability of individual MMP cells. When separated from the MMP, the cells cease to move and they no longer respond to magnetic fields. Viability tests indicated that, although several cells could separate from a MMP before completely losing their motility and viability, all of the separated cells were dead. Our data show that the high level of cellular organization in MMPs is essential for their motility, magnetotactic behavior, and viability. [Int Microbiol 2006; 9(4):267-272

Mitochondrial derivatives of culex quinquefasciatus (culicidae) spermatozoon : some new aspects evidenced by cytochemistry and image processing

Spermatozoa of the mosquito Culex quinquefasciatus have two mitochondrial derivatives of similar size and shape, containing a periodic matrix embedded by an amorphous region and surrounded by a membrane complex. The presence of cytochrome C oxidase activity was shown in the cortical zone. The use of the ethanolic-phosphotungstic acid technique suggests the presence of basic proteins in the paracrystalline structure. The analysis of the paracrystalline structure by digital image processing suggests that the cylindric-like subunits are empty structures and appear connected to each other by thin filaments. This approach showed that longitudinal filaments present an undulation disposition alongside the spermatozoon flagellum

Salinity dependence of the distribution of multicellular magnetotactic prokaryotes in a hypersaline lagoon

Candidatus Magnetoglobus multicellularis is an unusual magnetotactic multicellular microorganism composed of a highly organized assemblage of gram-negative bacterial cells. In this work, the salinity dependence of Ca. M. multicellularis and its abundance in the hypersaline Araruama Lagoon, Brazil were studied. Viability experiments showed that Ca. M. multicellularis died in salinities >55‰ and < 40‰. Low salinities were also observed to modify the cellular assemblage. In microcosms prepared with different salinities, the microorganism grew better at intermediate salinities whereas in high or low salinities, the size of the population did not increase over time. The concentrations of Ca. M. multicellularis in the lagoon were related to salinity; sites with lower and higher salinities than the lagoon average contained less Ca. M. multicellularis. These results demonstrate the influence of salinity on the survival and distribution of Ca. M. multicellularis in the environment. In sediments, the abundance of Ca. M. multicellularis ranged from 0 to 103 microorganisms/ml, which represented 0.001% of the counts of total bacteria. The ability of Ca. M. multicellularis to accumulate iron and sulfur in high numbers of magnetosomes (up to 905 per microorganism) suggests that its impact on the sequestration of these elements (0.1% for biogenic bacterial iron) is not proportional to its abundance in the lagoon. [Int Microbiol 2009; 12(3):193-201

Greigite magnetosome membrane ultrastructure in ‘Candidatus Magnetoglobus multicellularis’

The ultrastructure of the greigite magnetosome membrane in the multicellular magnetotactic bacteria ‘Candidatus Magnetoglobus multicellularis’ was studied. Each cell contains 80 membrane-enclosed iron-sulfide magnetosomes. Cytochemistry methods showed that the magnetosomes are enveloped by a structure whose staining pattern and dimensions are similar to those of the cytoplasmic membrane, indicating that the magnetosome membrane likely originates from the cytoplasmic membrane. Freeze-fracture showed intramembrane particles in the vesicles surrounding each magnetosome. Observations of cell membrane invaginations, the trilaminar membrane structure of immature magnetosomes, and empty vesicles together suggested that greigite magnetosome formation begins by invagination of the cell membrane, as has been proposed for magnetite magnetosomes

Spatiotemporal distribution of the magnetotactic multicellular prokaryote Candidatus Magnetoglobus multicellularis in a Brazilian hypersaline lagoon and in microcosms

Candidatus Magnetoglobus multicellularis is an unusual morphotype of magnetotactic prokaryotes. These microorganisms are composed of a spherical assemblage of gram-negative prokaryotic cells capable of swimming as a unitaligned along a magnetic field. While they occur in many aquatic habitats around the world, high numbers of Ca. M. multicellularishave been detected in Araruama Lagoon, a large hypersaline lagoon near the city of Rio de Janeiro, in Brazil. Here,we report on the spatiotemporal distribution of one such population in sediments of Araruama Lagoon, including its annualdistribution and its abundance compared with the total bacterial community. In microcosm experiments, Ca. M. multicellulariswas unable to survive for more than 45 days: the population density gradually decreased coinciding with a shift to theupper layers of the sediment. Nonetheless, Ca. M. multicellularis was detected throughout the year in all sites studied. Changes in the population density seemed to be related to the input of organic matter as well as to salinity. The populationdensity of Ca. M. multicellularis did not correlate with the total bacterial counts; instead, changes in the microbial communitystructure altered their counts in the environment. [Int Microbiol 2012; 15(3):141-149

Accumulation of Dry Matter and Morphological Composition of Irrigated Mombaça Grass Fertilized with and without Nitrogen under Grazing

Brazil is the holder of the largest commercial cattle herd in the world and the world\u27s leading exporter of fresh and industrialized meat. Beef production is based on pastures and the production system is influenced by absence of fertilization and the seasonality of forage during of this the year, caused mainly by temperature, rainfall and luminosity. Nitrogen (N) is the most important element for the development and growth of grasses, since it accelerates the formation and growth of new leaves, improves regrowth vigor resulting in greater production and carrying capacity of pastures (Cecato et al. 2011). The present study aimed to evaluate the accumulation of dry matter and percentage of leaf blade of irrigated Mombaça grass (Panicum maximum Jacq. cv. Mombaça) with four N fertilizer doses, under intermittent grazing

Uso e extrativismo de plantas medicinais pelos índios Fulni-ô no Nordeste do Brasil: implicações para a conservação local

The aims of this study were: to characterize the knowledge and traditional uses of two important medicinalplants from northeastern Brazil, Myracrodruon urundeuva (aroeira) and Sideroxylon obtusifolium (quixaba); to quantitativelyanalyze the bark collection process of these two species, and; to evaluate the population structure of these species in theOuricuri Forest, a native and sacred forest recognized as one of the collection sites of these resources. The study wasconducted in the Fulni-&ocirc; Indigenous Land (IL) located in the municipality of &Aacute;guas Belas, Pernambuco State. This studywas part of an ethnobotanical survey in the Fulni-&ocirc; IL and formed one of the lines of action of the project &ldquo;Studies for theEnvironmental and Cultural Sustainability of the Fulni-&ocirc; Medical System: Office of Medicinal Plant Care&rdquo;. In this study,344 semi-structured interviews were carried out between November 2007 and March 2008 from a stratified randomsample of the Fulni-&ocirc; population in the indian settlement (only including men and women over the age of 15). Theinterview script included specific questions regarding the interviewees&rsquo; knowledge and use of aroeira and quixaba. Toanalyze the population structure and level of exploitation of aroeira and quixaba populations, we used two complementarytechniques, 200-point quadrat sampling and walk-through sampling, in the Ouricuri Forest. Our data confirmed thataroeira is widely known by the Fulni-&ocirc;, while quixaba is known by fewer people in the community. Bark is the primaryplant part used by the indigenous population. During the collection of aroeira, for example, tree size is used as a selectivecriterion. Neither species exhibits the reverse J-shaped population structure typical of stable populations. Few adultindividuals are present, possibly due to selective logging targeted at such individuals. The two species studied here are alsoused for timber, increasing the pressure on their populations. Finally, despite the local scope of our findings, we brieflydiscuss their implications at both a local and a regional scale.Os objetivos deste estudo foram: caracterizar os conhecimentos e usos tradicionais de duas importantesesp&eacute;cies medicinais nativas do Nordeste do Brasil, Myracrodruon urundeuva (aroeira) e Sideroxylon obtusifolium (quixaba);analisar quantitativamente o processo de coleta de casca destas duas esp&eacute;cies; e avaliar a sua estrutura populacional naMata do Ouricuri, remanescente de floresta nativa e sagrada, reconhecida como um dos locais de coleta destes recursos. Oestudo foi realizado na Terra Ind&iacute;gena Fulni-&ocirc; (TIF), munic&iacute;pio de &Aacute;guas Belas, Pernambuco. Este estudo fez parte de umlevantamento etnobot&acirc;nico na TIF, sendo uma das linhas de a&ccedil;&atilde;o do projeto &ldquo;Estudos para a Sustentabilidade Ambientale Cultural do Sistema M&eacute;dico Fulni-&ocirc;: Oficina de Manipula&ccedil;&atilde;o de Plantas de Uso Medicinal&rdquo;. Neste estudo, 344 entrevistassemiestruturadas foram realizadas entre novembro de 2007 e mar&ccedil;o de 2008, utilizando-se uma amostra aleat&oacute;ria eestratificada da popula&ccedil;&atilde;o ind&iacute;gena da Aldeia Sede (incluindo apenas homens e mulheres com mais de 15 anos de idade). Oroteiro da entrevista considerou perguntas espec&iacute;ficas sobre o conhecimento e uso dos parceiros da pesquisa em rela&ccedil;&atilde;o &agrave;aroeira e quixaba. Para analisar a estrutura populacional e o n&iacute;vel de extra&ccedil;&atilde;o nas popula&ccedil;&otilde;es destas esp&eacute;cies usamos duast&eacute;cnicas complementares, a amostragem com 200 pontos quadrantes e o m&eacute;todo do caminhamento, na mata do Ouricuri.Nossos dados sustentam que a aroeira &eacute; amplamente conhecida pelos Fulni-&ocirc;, enquanto o quixaba &eacute; identificada porpoucas pessoas na comunidade. A casca &eacute; a principal parte da planta usada pela popula&ccedil;&atilde;o ind&iacute;gena. Especificamente paraa aroeira, o tamanho da &aacute;rvore &eacute; utilizado como um crit&eacute;rio seletivo. Nenhuma das duas esp&eacute;cies exibe a estruturapopulacional em forma de J-invertido, t&iacute;pico de popula&ccedil;&otilde;es est&aacute;veis. Poucos indiv&iacute;duos adultos foram amostrados,possivelmente devido &agrave; extra&ccedil;&atilde;o seletiva de madeira que foca tais indiv&iacute;duos. As duas esp&eacute;cies aqui estudadas tamb&eacute;m s&atilde;outilizadas para fins madeireiros, aumentando a press&atilde;o sobre suas popula&ccedil;&otilde;es. Finalmente, apesar do &acirc;mbito espec&iacute;fico de nossos resultados, discutimos brevemente as suas implica&ccedil;&otilde;es, tanto em n&iacute;vel local como em uma escala regional

Cristales biogénicos de magnetococos de la represa la fe y lago calima (colombia)

Con el propósito de estudiar la morfología y composición de magnetosomas sintetizados intracelularmente por magnetococos encontrados en la represa La Fe y lago Calima – Colombia, se separaron bacterias magnetotácticas (MTBs) por inducción magnética. MTBs y sus magnetosomas se evaluaron mediante espectroscopía de energías dispersivas de rayos X (EDX) usando microscopía electrónica de transmisión (TEM) para determinar el tamaño y la morfología de los nanocristales. Los resultados muestran una alta similitud entre los magnetosomas de los magnetococos estudiados, presentando cristales de magnetita con morfología hexagonal prismática y una media de longitud de 83 y 87 nm para cristales de La Fe y Calima respectivamente. Por el tamaño y factor de forma, los cristales se clasificaron en el rango de monodominio magnético. Los datos obtenidos permiten evidenciar futuras aplicaciones para la magnetita biogénica, en biotecnología y medicina