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Natural Sunlight Shapes Crude Oil-Degrading Bacterial Communities in Northern Gulf of Mexico Surface Waters.

Bacosa HP, Liu Z, Erdner DL - Front Microbiol (2015)

Bottom Line: Our results showed that, for treatments with oil and/or Corexit, sunlight significantly reduced bacterial diversity and evenness and was a key driver of shifts in bacterial community structure.In samples containing oil or dispersant, sunlight greatly reduced abundance of the Cyanobacterium Synechococcus but increased the relative abundances of Alteromonas, Marinobacter, Labrenzia, Sandarakinotalea, Bartonella, and Halomonas.For the first time, we demonstrated the effects of light in structuring microbial communities in water with oil and/or Corexit.

View Article: PubMed Central - PubMed

Affiliation: Marine Science Institute, The University of Texas at Austin Port Aransas, TX, USA.

ABSTRACT
Following the Deepwater Horizon (DWH) spill in 2010, an enormous amount of oil was observed in the deep and surface waters of the northern Gulf of Mexico. Surface waters are characterized by intense sunlight and high temperature during summer. While the oil-degrading bacterial communities in the deep-sea plume have been widely investigated, the effect of natural sunlight on those in oil polluted surface waters remains unexplored to date. In this study, we incubated surface water from the DWH site with amendments of crude oil, Corexit dispersant, or both for 36 days under natural sunlight in the northern Gulf of Mexico. The bacterial community was analyzed over time for total abundance, density of alkane and polycyclic aromatic hydrocarbon degraders, and community composition via pyrosequencing. Our results showed that, for treatments with oil and/or Corexit, sunlight significantly reduced bacterial diversity and evenness and was a key driver of shifts in bacterial community structure. In samples containing oil or dispersant, sunlight greatly reduced abundance of the Cyanobacterium Synechococcus but increased the relative abundances of Alteromonas, Marinobacter, Labrenzia, Sandarakinotalea, Bartonella, and Halomonas. Dark samples with oil were represented by members of Thalassobius, Winogradskyella, Alcanivorax, Formosa, Pseudomonas, Eubacterium, Erythrobacter, Natronocella, and Coxiella. Both oil and Corexit inhibited the Candidatus Pelagibacter with or without sunlight exposure. For the first time, we demonstrated the effects of light in structuring microbial communities in water with oil and/or Corexit. Overall, our findings improve understanding of oil pollution in surface water, and provide unequivocal evidence that sunlight is a key factor in determining bacterial community composition and dynamics in oil polluted marine waters.

No MeSH data available.


Related in: MedlinePlus

Shannon Wiener Index (H) and Evenness (E) of microbial communities. The indices represent the average of the time series (5, 10, 20, 27, 36 days). Error bar represents the standard deviation. Different letters are significantly different (p < 0.05) according to Tukey's HSD mean separation test.
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Figure 3: Shannon Wiener Index (H) and Evenness (E) of microbial communities. The indices represent the average of the time series (5, 10, 20, 27, 36 days). Error bar represents the standard deviation. Different letters are significantly different (p < 0.05) according to Tukey's HSD mean separation test.

Mentions: To compare how the bacterial diversity varied among treatments, we calculated the mean Shannon-Wiener index of diversity (H) and evenness (E) of the five sampling points for each treatment using the relative abundances at the genus level (Figure 3). Comparison of the mean H of the eight treatments revealed that the highest bacterial diversity was found in the light- and dark-seawater controls, followed by the amended dark treatments. The light treatments showed the lowest diversity. One-way ANOVA revealed that values for light treatments were significantly lower than the dark treatments (p < 0.01). Tukey's-HSD test of the means further revealed that diversities in dark and light controls do not vary significantly. However, diversities of light treatments with added oil and/or dispersant were statistically lower than the corresponding dark treatments. The evenness of the community followed the same pattern as the diversity index; light treatments were significantly less even than dark treatments in amended bottles. Overall, natural sunlight significantly reduced microbial diversity and evenness in the presence of oil and/or Corexit dispersant.


Natural Sunlight Shapes Crude Oil-Degrading Bacterial Communities in Northern Gulf of Mexico Surface Waters.

Bacosa HP, Liu Z, Erdner DL - Front Microbiol (2015)

Shannon Wiener Index (H) and Evenness (E) of microbial communities. The indices represent the average of the time series (5, 10, 20, 27, 36 days). Error bar represents the standard deviation. Different letters are significantly different (p < 0.05) according to Tukey's HSD mean separation test.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664628&req=5

Figure 3: Shannon Wiener Index (H) and Evenness (E) of microbial communities. The indices represent the average of the time series (5, 10, 20, 27, 36 days). Error bar represents the standard deviation. Different letters are significantly different (p < 0.05) according to Tukey's HSD mean separation test.
Mentions: To compare how the bacterial diversity varied among treatments, we calculated the mean Shannon-Wiener index of diversity (H) and evenness (E) of the five sampling points for each treatment using the relative abundances at the genus level (Figure 3). Comparison of the mean H of the eight treatments revealed that the highest bacterial diversity was found in the light- and dark-seawater controls, followed by the amended dark treatments. The light treatments showed the lowest diversity. One-way ANOVA revealed that values for light treatments were significantly lower than the dark treatments (p < 0.01). Tukey's-HSD test of the means further revealed that diversities in dark and light controls do not vary significantly. However, diversities of light treatments with added oil and/or dispersant were statistically lower than the corresponding dark treatments. The evenness of the community followed the same pattern as the diversity index; light treatments were significantly less even than dark treatments in amended bottles. Overall, natural sunlight significantly reduced microbial diversity and evenness in the presence of oil and/or Corexit dispersant.

Bottom Line: Our results showed that, for treatments with oil and/or Corexit, sunlight significantly reduced bacterial diversity and evenness and was a key driver of shifts in bacterial community structure.In samples containing oil or dispersant, sunlight greatly reduced abundance of the Cyanobacterium Synechococcus but increased the relative abundances of Alteromonas, Marinobacter, Labrenzia, Sandarakinotalea, Bartonella, and Halomonas.For the first time, we demonstrated the effects of light in structuring microbial communities in water with oil and/or Corexit.

View Article: PubMed Central - PubMed

Affiliation: Marine Science Institute, The University of Texas at Austin Port Aransas, TX, USA.

ABSTRACT
Following the Deepwater Horizon (DWH) spill in 2010, an enormous amount of oil was observed in the deep and surface waters of the northern Gulf of Mexico. Surface waters are characterized by intense sunlight and high temperature during summer. While the oil-degrading bacterial communities in the deep-sea plume have been widely investigated, the effect of natural sunlight on those in oil polluted surface waters remains unexplored to date. In this study, we incubated surface water from the DWH site with amendments of crude oil, Corexit dispersant, or both for 36 days under natural sunlight in the northern Gulf of Mexico. The bacterial community was analyzed over time for total abundance, density of alkane and polycyclic aromatic hydrocarbon degraders, and community composition via pyrosequencing. Our results showed that, for treatments with oil and/or Corexit, sunlight significantly reduced bacterial diversity and evenness and was a key driver of shifts in bacterial community structure. In samples containing oil or dispersant, sunlight greatly reduced abundance of the Cyanobacterium Synechococcus but increased the relative abundances of Alteromonas, Marinobacter, Labrenzia, Sandarakinotalea, Bartonella, and Halomonas. Dark samples with oil were represented by members of Thalassobius, Winogradskyella, Alcanivorax, Formosa, Pseudomonas, Eubacterium, Erythrobacter, Natronocella, and Coxiella. Both oil and Corexit inhibited the Candidatus Pelagibacter with or without sunlight exposure. For the first time, we demonstrated the effects of light in structuring microbial communities in water with oil and/or Corexit. Overall, our findings improve understanding of oil pollution in surface water, and provide unequivocal evidence that sunlight is a key factor in determining bacterial community composition and dynamics in oil polluted marine waters.

No MeSH data available.


Related in: MedlinePlus