Novel Bacterial Isolate from Permian Groundwater, Capable of Aggregating Potential Biofuel-Producing Microalga Nannochloropsis oceanica IMET1

Abstract

Increasing petroleum costs and climate change have resulted in microalgae receiving attention as potential biofuel producers. Little information is available on the diversity and functions of bacterial communities associated with biofuel-producing algae. A potential biofuel-producing microalgal strain, Nannochloropsis oceanica IMET1, was grown in Permian groundwater. Changes in the bacterial community structure at three temperatures were monitored by two culture-independent methods, and culturable bacteria were characterized. After 9 days of incubation, N. oceanica IMET1 began to aggregate and precipitate in cultures grown at 30°C, whereas cells remained uniformly distributed at 15°C and 25°C. The bacterial communities in cultures at 30°C changed markedly. Some bacteria isolated only at 30°C were tested for their potential for aggregating microalgae. A novel bacterium designated HW001 showed a remarkable ability to aggregate N. oceanica IMET1, causing microalgal cells to aggregate after 3 days of incubation, while the total lipid content of the microalgal cells was not affected. Direct interaction of HW001 and N. oceanica is necessary for aggregation. HW001 can also aggregate the microalgae N. oceanica CT-1, Tetraselmis suecica, and T. chuii as well as the cyanobacterium Synechococcus WH8007. 16S rRNA gene sequence comparisons indicated the great novelty of this strain, which exhibited only 89% sequence similarity with any previously cultured bacteria. Specific primers targeted to HW001 revealed that the strain originated from the Permian groundwater. This study of the bacterial communities associated with potential biofuel-producing microalgae addresses a little-investigated area of microalgal biofuel research and provides a novel approach to harvest biofuel-producing microalgae by using the novel bacterium strain HW001.

Effects of bacterial communities on biofuel-producing microalgae: stimulation, inhibition and harvesting

“…We investigated the diversity of bacterial communities associated with the biofuel-producing microalga Nannochloropsis oceanica IMET1 grown at different temperatures by a culture-dependent approach as well as the culture-independent methods, DGGE and 16S rRNA gene based clone library community analysis (Wang et al, 2012). The three methods gave the consistent result that bacterial communities varied at different temperatures and changed dramatically with the algae growing at a high temperature of 30 C. Alphaproteobacteria, Gammaproteobacteria and Bacteroidetes dominated in all the clone libraries.…”

“…In cultivation systems, the higher microalgal growth rate can increase the microalgae/bacteria ratio to 1:10. In our Nannochloropsis cultures grown on a small scale, microalgal cell densities reached 10 7 -10 8 cells/mL in a photobioreactor system, with bacterial counts reaching up to 10 8 -10 9 cells/mL (Wang et al, 2012).…”

Phylogenetic diversity of bacterial communities associated with bioremediation of crude oil in microcosms

“…Pellets were then applied for extracting total genomic DNA by using the Mobio Soil DNA Extraction Kit (MoBio Laboratories, Solana Beach, CA). Bacterial communities were analyzed both before and after bioremediation by two culture-independent methods, denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene based clone library community analysis, as described by Wang et al (Mohamed et al, 2008;Wang et al, 2012).…”

Permianibacter aggregans gen. nov., sp. nov., a bacterium of the family Pseudomonadaceae capable of aggregating potential biofuel-producing microalgae

“…Here, a bacterial strain, affiliated into the family Pseudomonadaceae and showing a distinct function is described. The strain, designated HW001 T was isolated from the phycosphere of the potential biofuel-producing microalgae Nannochloropsis oceanica IMET1 in a study investigating the diversity and functions of the bacterial communities associated with this microalga (Wang et al, 2012). Strain HW001 T showed a remarkable ability to aggregate N. oceanica IMET1, which could be a novel approach to harvest biofuel-producing microalgae.…”