Coral reefs: Rainforests of the sea

Honors College, Washington State UniversityYost, Denise M. Coral reefs: rainforests of the sea, Washington State University Honors College thesis, Spring 200

Variability of Symbiodinium Communities in Waters, Sediments, and Corals of Thermally Distinct Reef Pools in American Samoa.

Reef-building corals host assemblages of symbiotic algae (Symbiodinium spp.) whose diversity and abundance may fluctuate under different conditions, potentially facilitating acclimatization to environmental change. The composition of free-living Symbiodinium in reef waters and sediments may also be environmentally labile and may influence symbiotic assemblages by mediating supply and dispersal. The magnitude and spatial scales of environmental influence over Symbiodinium composition in different reef habitat compartments are, however, not well understood. We used pyrosequencing to compare Symbiodinium in sediments, water, and ten coral species between two backreef pools in American Samoa with contrasting thermal environments. We found distinct compartmental assemblages of clades A, C, D, F, and/or G Symbiodinium types, with strong differences between pools in water, sediments, and two coral species. In the pool with higher and more variable temperatures, abundance of various clade A and C types differed compared to the other pool, while abundance of D types was lower in sediments but higher in water and in Pavona venosa, revealing an altered habitat distribution and potential linkages among compartments. The lack of between-pool effects in other coral species was due to either low overall variability (in the case of Porites) or high within-pool variability. Symbiodinium communities in water and sediment also showed within-pool structure, indicating that environmental influences may operate over multiple, small spatial scales. This work suggests that Symbiodinium composition is highly labile in reef waters, sediments, and some corals, but the underlying drivers and functional consequences of this plasticity require further testing with high spatial resolution biological and environmental sampling

Data from: Variability of Symbiodinium communities in waters, sediments, and corals of thermally distinct reef pools in American Samoa

Reef-building corals host assemblages of symbiotic algae (Symbiodinium spp.) whose diversity and abundance may fluctuate under different conditions, potentially facilitating acclimatization to environmental change. The composition of free-living Symbiodinium in reef waters and sediments may also be environmentally labile and may influence symbiotic assemblages by mediating supply and dispersal. The magnitude and spatial scales of environmental influence over Symbiodinium composition in different reef habitat compartments are, however, not well understood. We used pyrosequencing to compare Symbiodinium in sediments, water, and ten coral species between two backreef pools in American Samoa with contrasting thermal environments. We found distinct compartmental assemblages of clades A, C, D, F, and/or G Symbiodinium types, with strong differences between pools in water, sediments, and two coral species. In the pool with higher and more variable temperatures, abundance of various clade A and C types differed compared to the other pool, while abundance of D types was lower in sediments but higher in water and in Pavona venosa, revealing an altered habitat distribution and potential linkages among compartments. The lack of between-pool effects in other coral species was due to either low overall variability (in the case of Porites) or high within-pool variability. Symbiodinium communities in water and sediment also showed within-pool structure, indicating that environmental influences may operate over multiple, small spatial scales. This work suggests that Symbiodinium composition is highly labile in reef waters, sediments, and some corals, but the underlying drivers and functional consequences of this plasticity require further testing with high spatial resolution biological and environmental sampling

Characterization of a Gene Family of Outer Membrane Proteins (ropB) in Rhizobium leguminosarum bv. viciae VF39SM and the Role of the Sensor Kinase ChvG in Their Regulation ▿

The outer membrane of Gram-negative bacteria represents the interface between the bacterium and its external environment. It has a critical role as a protective barrier against harmful substances and is also important in host-bacteria interactions representing the initial physical point of contact between the host cell and bacterial cell. RopB is a previously identified outer membrane protein from Rhizobium leguminosarum bv. viciae that is present in free-living cells but absent in bacteroids (H. P. Roest, I. H. Mulders, C. A. Wijffelman, and B. J. Lugtenberg, Mol. Plant Microbe Interact. 8:576-583, 1995). The functions of RopB and the molecular mechanisms of ropB gene regulation have remained unknown. We identified and cloned ropB and two homologs (ropB2 and ropB3) from the R. leguminosarum VF39SM genome. Reporter gene fusions indicated that the expression of ropB was 8-fold higher when cells were grown in complex media than when they were grown in minimal media, while ropB3 expression was constitutively expressed at low levels in both complex and minimal media. Expression of ropB2 was negligible under all conditions tested. The use of minimal media supplemented with various sources of peptides resulted in a 5-fold increase in ropB expression. An increase in ropB expression in the presence of peptides was not observed in a chvG mutant background, indicating a role for the sensor kinase in regulating ropB expression. Each member of the ropB gene family was mutated using insertional mutagenesis, and the mutants were assayed for susceptibility to antimicrobial agents and symbiotic phenotypes. All mutants formed effective nodules on pea plants, and gene expression for each rop gene in bacteroids was negligible. The functions of ropB2 and ropB3 remain cryptic, while the ropB mutant had an increased sensitivity to detergents, hydrophobic antibiotics, and weak organic acids, suggesting a role for RopB in outer membrane stability

Cunning_PLoSONE_Dryad_Archive

This archive file contains all data and scripts necessary to reproduce the analyses and figures presented in this manuscript

<i>Symbiodinium</i> clade composition for complete dataset.

<p>Bars represent the proportion of sequences in each sample from each clade.</p

Altered compartmental distributions of <i>Symbiodinium</i> between pools.

<p>The inner ring shows <i>Symbiodinium</i> taxa (clade A = green, C = yellow, D = purple, F = red, G = orange) that were differentially abundant in each compartment (middle ring: water = blue, sediment = gray, coral = pink, <i>Pavona venosa</i> = Pv, <i>Psammocora contigua</i> = Pc) between pools. The outer ring indicates whether taxa were more or less abundant in each pool, and ribbons connect instances where taxa were differentially abundant in multiple compartments. Ribbons reveal different compartmental distributions of taxa in each pool: in pool 300 (vs. 400), 8 taxa (including 4 clade D) were less abundant in sediments and more abundant in water and/or coral, while 2 other clade C taxa were more abundant in sediments and less abundant in water.</p

Location and <i>Symbiodinium</i> clade composition of water, coral, and sediment samples in each pool.

<p>Points represent sample positions and pie charts represent clade composition (A = green, C = yellow, D = purple, F = red, G = orange). Water samples (A) showed more clade A near shore, while sediments (C) showed more clade A further from shore, and clusters of more similar communities (e.g., clades D and F in the northeast and clade G in the southwest corners of pool 300; similar mixtures of C, D, and A in northwest corner of pool 400). Corals (B) tended to have more clade D near pool edges, especially in pool 400. Clade composition for <i>Porites</i> spp. (i.e., species with the lowest dissimilarity, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0145099#pone.0145099.t001" target="_blank">Table 1</a>) is not shown here, but can be seen in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0145099#pone.0145099.g001" target="_blank">Fig 1</a>. While data are visualized at the clade level, spatial autocorrelation tests reflect patterns in total diversity.</p