Diatom-Associated Bacteria Report
Exploring the diversity, abundance, and variability of diatom-associated bacteria in the oligotrophic ocean
I. Abstract
The ecology of diatoms may be better explained by conceptualizing them as composite organisms consisting of the host cell and its bacterial associates. Our previous investigated diatom-bacterial interactions at the single-cell level found that bacterial assemblages varied substantially even among closely related individual host cells. The bacterial assemblages associated with single cells could be separated into three distinct groups, but these groups occurred irrespective of host cell identity. Instead, the distinct groups were best explained by strong interactions among host-associated bacteria; for example, in one group, …show more content…
Multiple strains of Alteromonas and Marinobacter were isolated from the same Chaetoceros host. Individual strains were added to three different xenic diatom hosts (the origin host, a naïve Chaetoceros host, and a naïve Amphipora host), to evaluate whether perturbations in their bacterial consortia could affect host growth, carrying capacity, and decline. Additionally, inoculations were repeated in vitamin-rich and vitamin-poor media to test whether the added bacteria provided B-vitamins to their host. Manipulating the bacterial consortia had a strong effect on the naïve Chaetoceros host cell, but minimal effects were observed for the origin Chaetoceros host or the more distantly related Amphipora host. These results demonstrate that the relationship may differ between congeners, and that host-associated bacterial consortia may have limited resilience or resistance to perturbation. Finally, a metagenomic analysis of the original amplified genomes of single diatom cells plus their associated bacteria was performed to gain a better understanding of the functional capabilities contributed by bacteria to a diatom-bacterial association in nature. Six diatom cells derived from two of the three distinct …show more content…
The carbon fixed by oceanic diatoms is equivalent to the organic carbon produced by all of the terrestrial rainforests combined (Nelson et al. 1995). Diatoms not only generate organic carbon from carbon dioxide, but also play a major role in the ‘biological pump’, wherein nutrients (N, P, Fe, Si, trace metals) are taken up in the euphotic zone and sink to the benthos as biological material incorporated into fecal pellets or marine snow. Nearly half of the sinking organic carbon produced by diatoms is consumed by bacteria and remineralized into the upper ocean as inorganic nutrients, a process referred to as the microbial loop (Azam et al. 1983). Microbial remineralization is essential to maintain nutrients in this system (Williams and Yentsch 1976; Cole 1982), including silica, which otherwise may limit diatom growth (Bidle et al.
I. Abstract
The ecology of diatoms may be better explained by conceptualizing them as composite organisms consisting of the host cell and its bacterial associates. Our previous investigated diatom-bacterial interactions at the single-cell level found that bacterial assemblages varied substantially even among closely related individual host cells. The bacterial assemblages associated with single cells could be separated into three distinct groups, but these groups occurred irrespective of host cell identity. Instead, the distinct groups were best explained by strong interactions among host-associated bacteria; for example, in one group, …show more content…
Multiple strains of Alteromonas and Marinobacter were isolated from the same Chaetoceros host. Individual strains were added to three different xenic diatom hosts (the origin host, a naïve Chaetoceros host, and a naïve Amphipora host), to evaluate whether perturbations in their bacterial consortia could affect host growth, carrying capacity, and decline. Additionally, inoculations were repeated in vitamin-rich and vitamin-poor media to test whether the added bacteria provided B-vitamins to their host. Manipulating the bacterial consortia had a strong effect on the naïve Chaetoceros host cell, but minimal effects were observed for the origin Chaetoceros host or the more distantly related Amphipora host. These results demonstrate that the relationship may differ between congeners, and that host-associated bacterial consortia may have limited resilience or resistance to perturbation. Finally, a metagenomic analysis of the original amplified genomes of single diatom cells plus their associated bacteria was performed to gain a better understanding of the functional capabilities contributed by bacteria to a diatom-bacterial association in nature. Six diatom cells derived from two of the three distinct …show more content…
The carbon fixed by oceanic diatoms is equivalent to the organic carbon produced by all of the terrestrial rainforests combined (Nelson et al. 1995). Diatoms not only generate organic carbon from carbon dioxide, but also play a major role in the ‘biological pump’, wherein nutrients (N, P, Fe, Si, trace metals) are taken up in the euphotic zone and sink to the benthos as biological material incorporated into fecal pellets or marine snow. Nearly half of the sinking organic carbon produced by diatoms is consumed by bacteria and remineralized into the upper ocean as inorganic nutrients, a process referred to as the microbial loop (Azam et al. 1983). Microbial remineralization is essential to maintain nutrients in this system (Williams and Yentsch 1976; Cole 1982), including silica, which otherwise may limit diatom growth (Bidle et al.