Tag Archives: purple sulfur bacteria

Check out our newest paper in PLoS ONE!

Temporal and Spatial Distribution of the Microbial Community of Winogradsky Columns

Winogradsky columns are model microbial ecosystems prepared by adding pond sediment to a clear cylinder with additional supplements and incubated with light. Environmental gradients develop within the column creating diverse niches that allow enrichment of specific bacteria. The enrichment culture can be used to study soil and sediment microbial community structure and function. In this study we used a 16S rRNA gene survey to characterize the microbial community dynamics during Winogradsky column development to determine the rate and extent of change from the source sediment community. Over a period of 60 days, the microbial community changed from the founding pond sediment population: Cyanobacteria, Chloroflexi, Nitrospirae, and Planctomycetes increased in relative abundance over time, while most Proteobacteria decreased in relative abundance. A unique, light-dependent surface biofilm community formed by 60 days that was less diverse and dominated by a few highly abundant bacteria. 67–72% of the surface community was comprised of highly enriched taxa that were rare in the source pond sediment, including the Cyanobacteria Anabaena, a member of the Gemmatimonadetes phylum, and a member of the Chloroflexi class Anaerolinea. This indicates that rare taxa can become abundant under appropriate environmental conditions and supports the hypothesis that rare taxa serve as a microbial seed bank. We also present preliminary findings that suggest that bacteriophages may be active in the Winogradsky community. The dynamics of certain taxa, most notably the Cyanobacteria, showed a bloom-and-decline pattern, consistent with bacteriophage predation as predicted in the kill-the-winner hypothesis. Time-lapse photography also supported the possibility of bacteriophage activity, revealing a pattern of colony clearance similar to formation of viral plaques. The Winogradsky column, a technique developed early in the history of microbial ecology to enrich soil microbes, may therefore be a useful model system to investigate both microbial and viral ecology.


Watching Bacteria Grow: Winogradsky Panel Day 7

The panel is changing more slowly now, but the oranges and greens are getting richer and the sulfur-enriched mud is showing more and coalescing black spots.
IMG_5962The level of the mud dropped overnight.  This could be due to settling of the mud and/or release of gas bubbles.  There are some water-filled gaps, and the water level is lower.  There is now air above the entire length of the water surface, instead of just at the opening of the panel (top left).  Note that there is also a left to right gradient in the water, which was already present before settling.  Near the opening, there is brownish/red colonies growing on the walls, probably aerobes (requires oxygen) explaining why its not present further from the opening.  The water is murky from left to right, perhaps microbes that can tolerate low levels of oxygen, up to a point near the right side where the water layer is still clear.




Watching Bacteria Grow: Winogradsky Panel Day 4

The Winogradsky panel is developing much more quickly than I had expected. Differences are noticeable from day to day.

The panel at day 4.

The colors at the interface are richer and thicker. The green sulfur bacteria below the orange layer are more obvious now.

IMG_5937The modified mud layer now has more black spots and there are now some bright green spots, probably green sulfur bacteria.  GSB are more tolerant of high H2S concentrations than the purple sulfur bacteria, so are growing well in the areas where the black spots tell us there is H2S.  Note the gas bubbles at the bottom center of the image.  The squiggly lines are actually paths left behind by the movement of small, red larvae of midge flies, called blood worms.  They made their way up to the top, and are now all apparently dead.  (And will be food for some bacteria).