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martes, 27 de octubre de 2009

Metabolism, cell growth and the bacterial cell cycle



The life of a bacterial cell is feast or famine. To survive the bacterium must rapidly adapt to changing environmental conditions. Colonization of the mammalian gut provides an enteric organism with an abundant source of carbohydrates, whereas a flash flood instantly depletes the nutrient supply for a soil bacterium. Nutrient-rich conditions lead to a decrease in mass doubling time and an increase in cell size, whereas nutrient-poor conditions curtail growth and reduce cell size. Changes in growth rate must be accompanied by changes in the cell cycle to ensure that cell division stays coordinated with mass doubling, chromosome replication and chromosome segregation. How organisms adjust their cell cycle dynamics to compensate for changes in nutritional conditions is an important outstanding question in bacterial physiology. Recent work suggests that multiple signalling pathways transmit nutritional and growth rate information directly to the cell cycle machinery. Multiple signalling pathways permit cells to constantly sample their environments and fine-tune cell cycle processes, a substantial advantage under challenging conditions.
Adaptation to fluctuations in nutrient availability is a fact of life for single-celled organisms in the ‘wild’. A decade ago our understanding of how bacteria adjust cell cycle parameters to accommodate changes in nutrient availability stemmed almost entirely from elegant physiological studies completed in the 1960s. This article summarizes recent groundbreaking work in this area and discuss potential mechanisms by which nutrient availability and metabolic status are coordinated with cell growth, chromosome replication and cell division.
Metabolism, cell growth and the bacterial cell cycle. Nature Reviews Microbiology 7, 822 (2009)
Related:
Bacterial Chemoreceptors
A day in the life of a cyanobacterium
How smart are bacteria?

domingo, 25 de octubre de 2009

La ciencia no está aislada... La microbiología si que menos


endotelinas sent you a video: "Protozoarios 2"

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Protozoarios - 2 parte
Protozoarios 2
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Protozoos - Introduction
mundo microscópico
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Los protozoarios
Protozoarios 1
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Morfologia Bacteriana Y Tinciones Diferenciales

A manera de repaso...

sábado, 17 de octubre de 2009

Virología - Sesión 2

Virología 2
Universidad Católica de Oriente - Facultad de Educación
Curso: Microbiología – Sesión # 12
Docente: Esp. Juan Carlos González Sánchez M.D.
Octubre 17 de 2009
Tópico: Morfología viral y clasificación

DESARROLLO DE LA SESIÓN.
1. Generalidades de los Virus: Terminanos la lectura comentada del texto sobre generalidades http://www.facmed.unam.mx/deptos/microbiologia/virologia/generalidades.php

2. Revisión de la presentación:

TRABAJO AUTONOMO.
a. Cada uno presentará una síntesis del tema, en el formato que desee.
b. Desarrollar una prueba de evaluación sobre el tema, presentarla en la próxima sesión, una formulario con solucionario y otro en blanco

Teacher JC
Facultad de Educación Universidad Católica de Oriente
Biotecnología y Enseñabilidad

lunes, 12 de octubre de 2009

Bacterial Chemoreceptors



Chemoreceptors are key components of the high-performance signal transduction system that controls bacterial chemotaxis. Chemoreceptors are typically localized in a cluster at the cell pole, where interactions among the receptors in the cluster are thought to contribute to the high sensitivity, wide dynamic range, and precise adaptation of the signaling system. Previous structural and genomic studies have produced conflicting models, however, for the arrangement of the chemoreceptors in the clusters. Using whole-cell electron cryo-tomography, here we show that chemoreceptors of different classes and in many different species representing several major bacterial phyla are all arranged into a highly conserved, 12-nm hexagonal array consistent with the proposed “trimer of dimers” organization. The various observed lengths of the receptors confirm current models for the methylation, flexible bundle, signaling, and linker sub-domains in vivo. Our results suggest that the basic mechanism and function of receptor clustering is universal among bacterial species and was thus conserved during evolution.
Universal architecture of bacterial chemoreceptor arrays. PNAS USA September 23 2009 doi: 10.1073/pnas.0905181106
Related:
Bacterial Motility
Super-Resolution Light Microscopy of Escherichia coli
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domingo, 11 de octubre de 2009

Liver flukes and cancer

Liver flukes and cancer

Liver fluke Scientists have found that the human liver fluke (Opisthorchis viverrini) contributes to the development of bile duct (liver) cancer by secreting granulin, a growth hormone that is known to cause uncontrolled growth of cells. It was known that O. viverrini secreted a protein that caused cell growth, but the identity of the protein was unknown. It was also known that the parasite secreted granulin but we did not know that it could affect the human cells around it. Scientists used E. coli bacteria to express the O. viverrini granulin, which was shown to induce proliferation in mouse fibroblast cells and human bile duct cancer cells in the absence of the parasite. Proliferation of the cells was halted by adding anti-granulin antibody, proving granulin's role in producing a cancerous environment.

The International Agency for Research on Cancer classifies the human liver fluke as a Group I Carcinogen, meaning that O. viverrini is a proven cause of cancer. In northern Thailand, where the liver fluke is most common, more than 7 million people are infected at any given time. Previously, it was thought that the cancer was caused by the physical damage brought about by the fluke feeding on cells lining the bile ducts, as well as a diet high in nitrosamines from fermented fish (a native dish of Thailand). The paper suggests that the granulin secreted by the parasite is a major contributing factor to developing bile duct cancer. This discovery leads the way to a better understanding of how liver flukes cause such a devastating form of cancer.

A Granulin-Like Growth Factor Secreted by the Carcinogenic Liver Fluke, Opisthorchis viverrini, Promotes Proliferation of Host Cells. PLoS Pathog 5(10): e100061 doi:10.1371/journal.ppat.1000611
The human liver fluke, Opisthorchis viverrini, infects millions of people throughout south-east Asia and is a major cause of cholangiocarcinoma, or cancer of the bile ducts. The mechanisms by which chronic infection with O. viverrini results in cholangiocarcinogenesis are multi-factorial, but one such mechanism is the secretion of parasite proteins with mitogenic properties into the bile ducts, driving cell proliferation and creating a tumorigenic environment. Using a proteomic approach, we identified a homologue of human granulin, a potent growth factor involved in cell proliferation and wound healing, in the excretory/secretory (ES) products of the parasite. O. viverrini granulin, termed Ov-GRN-1, was expressed in most parasite tissues, particularly the gut and tegument. Furthermore, Ov-GRN-1 was detected in situ on the surface of biliary epithelial cells of hamsters experimentally infected with O. viverrini. Recombinant Ov-GRN-1 was expressed in E. coli and refolded from inclusion bodies. Refolded protein stimulated proliferation of murine fibroblasts at nanomolar concentrations, and proliferation was inhibited by the MAPK kinase inhibitor, U0126. Antibodies raised to recombinant Ov- GRN-1 inhibited the ability of O. viverrini ES products to induce proliferation of murine fibroblasts and a human cholangiocarcinoma cell line in vitro, indicating that Ov-GRN-1 is the major growth factor present in O. viverrini ES products. This is the first report of a secreted growth factor from a parasitic worm that induces proliferation of host cells, and supports a role for this fluke protein in establishment of a tumorigenic environment that may ultimately manifest as cholangiocarcinoma.

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Tomado de microbiologybytes, url: http://www.microbiologybytes.com/blog/2009/10/09/liver-flukes-and-cancer/ cited on Sep 11/09

--
JC Teacher

La ciencia crece en colectividad, no asiladamente...

"Si alcancé a ver tan lejos fue porque me subí a hombros de gigantes", decía Newton en recuerdo que sus grandes maestros. En una actividad colectiva como la Ciencia, donde todos los saberes están en constante revisión, es fundamental conocer la historia de las descubrimientos, de las teorías y de las personas que estaban tras ellas.
--
JC Teacher

viernes, 9 de octubre de 2009


Microbiología aplicada....

Virología

Universidad Católica de Oriente - Facultad de Educación
Curso: Microbiología – Sesión # 11
Docente: Esp. Juan Carlos González Sánchez M.D.
Octubre 10 de 2009
Tópico: Virología

1. Historia de los virus
2. Morfología viral y clasificación
3. Hábitat y formas de evidenciar los virus Morfología
4. Clasificación

DESARROLLO DE LA SESIÓN.
1. Generalidades de los Virus:
Leemos y discutimos juntos la siguiente lectura: Virología – Generalidades
http://www.facmed.unam.mx/deptos/microbiologia/virologia/generalidades.php
2. Discusión de la siguiente presentación:
http://www.microcsalud.us.es/asignaturas/enfermeria/temas/TEMA%2016%20GENERALIDADES.ppt

3. Cada uno presentará una síntesis del tema, en el formato que desee.

4. Material Complementario: http://www.scribd.com/doc/19492372/CLASE-1-GENERALIDADES-VIROLOGIA

5. Trabajo Autónomo:
5.1 Desarrollar una prueba de evaluación sobre el tema, presentarla en la próxima sesión.
5.2 Presentar un esquema donde se muestre el ciclo reproductivo de un virus.

Teacher JC
Facultad de Educación Universidad Católica de Oriente

sábado, 3 de octubre de 2009

Ciclo Celular




Cuadro Sinóptico, tomado del blog de Hernán Darío Ramírez, url: http://ramirezrhernan.blogspot.com/


Nota: Corregir las impresiones ortográficas en Fases...çç


JC

Generalidades de la Microbiología


Cuadro Sinóptico, tomado del blog de Hernán Darío Ramírez, url: http://ramirezrhernan.blogspot.com/


MICROSCOPIO OPTICO


felicitaciones! Erika


TINCIÓN DE GRAMM




Cinco Reinos Seres Vivos


viernes, 2 de octubre de 2009

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Clasificación de los seres vivos

JC
breve descripción de los 5 reinos en los que estan clasificados los seres vivos que forman parte de nuestra biodiversidad
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endotelinas sent you a video: "El Reino de los Hongos"

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A manera de síntesis

JC
El Reino Fungi o Reino de los Hongos comprende varios tipos de "extraños seres" que no son plantas ni animales. No hacen la fotosíntesis, sino que necesitan alimentarse de materia orgánica que descomponen. Se reproducen por esporas. Hay especies perjudiciales y otras muy beneficiosas para el ser humano.
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Micología

Universidad Católica de Oriente - Facultad de Educación
Curso: Microbiología - Sesión * Docente: Esp. Juan Carlos González Sánchez
Octubre 3 de 2009 * Tópico: Micología

1. Generalidades.
2. Clasificación - Reproducción.
3. Micosis a nivel clínico
4. Aplicaciones


Actividades:

Revisar cada uno de los enlaces, en su portafolio o blog, presente un resumen – en el formato que prefiera – donde consigne una síntesis de la información revisada

1. Micología: Generalidades. http://www.slideshare.net/franciskoleon/generalidades-hongos
http://www.slideshare.net/furia/micologa-generalidades
2. Micología: Clasificación – Reproducción
http://200.93.199.34/areas_academicas/biology/multimedia/presentaciones/quintoquibio/hongos.ppt
www.uprm.edu/biology/cursos/biologiageneral/OClab5.ppt
COMPLEMENTARIO: http://mail.fq.edu.uy/~microbio/MGral/T2007/hongos1.pdf
3. Micosis a nivel clínico
http://hsjd08.files.wordpress.com/2008/03/04-generalidades-de-hongos.ppt
4. Micología – Aplicaciones
http://html.rincondelvago.com/algas-y-hongos.html Parte final del documento.

Teacher JC
Facultad de Educación Universidad Católica de Oriente