MicrobiologyBytes

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Joe DeRisi talks about amazing new ways to diagnose viruses (and treat the illnesses they cause) using DNA. His work may help us understand malaria, SARS, avian flu – and the 60 percent of everyday viral infections that go undiagnosed.

Dr. Peter Palese describes how reconstructing the extinct 1918 pandemic influenza virus by reverse genetics can help us better understand molecular basis of virulence and the mechanisms by which pandemic influenza viruses are transmitted.

When fish school, birds flock, insects and bacteria swarm, a population of similar individuals cruises along similar, sometimes cyclic, paths. How do the members of a swarm anticipate the movement of others to coordinate movement with them? And how do members, when each is moving rapidly near to others, avoid impeding their neighbor’s motion? These general issues, which have yet to be resolved for any schooling, flocking, or swarming organism, can be investigated in swarming bacteria. Such investigation might have practical value because swarming enables pathogens like Proteus, for example, to invade the urinary tract and to spread along the surface of catheters placed in the urethra. The behavior of swarming individuals might also suggest ways to speed high density automobile or pedestrian traffic and ways to avoid traffic jams. Bacterial sensory systems and behaviors are more amenable to analysis than those of animals. Because they are relatively small; several thousand bacteria can be followed in a time lapse movie of a swarm. Among bacteria that swarm are the hyperflagellated bacteria, all of the Myxobacteria, which lack flagella, and the Bacteriodetes that include Cytophaga, Flavobacteria, and Bacteriodes. Millions of Myxococcus xanthus cells are found to swarm outward for more than a week at a steady rate of approximately 0.1 mm/hr, a rate close to half the speed of individual cell movement. Swarming gives them a significant growth advantage: Whereas cells in the swarmcenter are competing with each other for nutrient and oxygen, cells at the swarm edge have practically unfettered access to both.

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Periodic reversal of direction allows Myxobacteria to swarm. PNAS USA January 21, 2009

Many bacteria can rapidly traverse surfaces from which they are extracting nutrient for growth. They generate flat, spreading colonies, called swarms because they resemble swarms of insects. We seek to understand how members of any dense swarm spread efficiently while being able to perceive and interfere minimally with the motion of others. To this end, we investigate swarms of the myxobacterium, Myxococcus xanthus. Individual M. xanthus cells are elongated; they always move in the direction of their long axis; and they are in constant motion, repeatedly touching each other. Remarkably, they regularly reverse their gliding directions. We have constructed a detailed cell- and behavior-based computational model of M. xanthus swarming that allows the organization of cells to be computed. By using the model, we are able to show that reversals of gliding direction are essential for swarming and that reversals increase the outflow of cells across the edge of the swarm. Cells at the swarm edge gain maximum exposure to nutrient and oxygen. We also find that the reversal period predicted to maximize the outflow of cells is the same (within the errors of measurement) as the period observed in experiments with normal M. xanthus cells. This coincidence suggests that the circuit regulating reversals evolved to its current sensitivity under selection for growth achieved by swarming. Finally, we observe that, with time, reversals increase the cell alignment, and generate clusters of parallel cells.

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• The Hybrid Two-Engine System of Myxobacteria
• Bacterial Motility
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• Communication, cooperation, competition and cheating – bacteria are just like us

Asteroid strikes get all the coverage, but “Medea Hypothesis” author Peter Ward argues that most of Earth’s mass extinctions were caused by lowly bacteria. The culprit, a poison called hydrogen sulfide, may have an interesting application in medicine.

What is genomics? How will it affect our lives? In this primer on the genomics revolution, entrepreneur Barry Schuler says we can at least expect healthier, tastier food. He suggests we start with the pinot noir grape, to build better wines.

MicrobiologyBytes has discussed before Craig Venter’s attempts to create a synthetic microorganism. In 2008, Venter described his work at the TED Conference, and his talk is well worth watching:

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• Mycoplasma laboratorium, the first synthetic organism
• The end of the world? Dr Franken-Venter?

Nice microbiology video from the Royal Sussex County Hospital NHS Trust.

Following on from the microscope basics video series, YouTube user lgines continues to produce the goods with a useful series of videos on aseptic technique:

Preparing a bacterial culture (broth to broth):

Preparing a bacterial culture (broth to plate):

Preparing a bacterial culture (slant to plate):

Preparing a smear from a broth culture:

Performing an isolation streak:

Gram staining:

Related:

• Microscope basics video series