Use of De Novo Transcriptome Libraries to Characterize a Novel Oleaginous Marine Chlorella Species during the Accumulation of Triacylglycerols

Abstract

Marine chlorophytes of the genus Chlorella are unicellular algae capable of accumulating a high proportion of cellular lipids that can be used for biodiesel production. In this study, we examined the broad physiological capabilities of a subtropical strain (C596) of Chlorella sp. “SAG-211-18” including its heterotrophic growth and tolerance to low salt. We found that the alga replicates more slowly at diluted salt concentrations and can grow on a wide range of carbon substrates in the dark. We then sequenced the RNA of Chlorella strain C596 to elucidate key metabolic genes and investigate the transcriptomic response of the organism when transitioning from a nutrient-replete to a nutrient-deficient condition when neutral lipids accumulate. Specific transcripts encoding for enzymes involved in both starch and lipid biosynthesis, among others, were up-regulated as the cultures transitioned into a lipid-accumulating state whereas photosynthesis-related genes were down-regulated. Transcripts encoding for two of the up-regulated enzymes—a galactoglycerolipid lipase and a diacylglyceride acyltransferase—were also monitored by reverse transcription quantitative polymerase chain reaction assays. The results of these assays confirmed the transcriptome-sequencing data. The present transcriptomic study will assist in the greater understanding, more effective application, and efficient design of Chlorella-based biofuel production systems.

A downstream box fusion allows stable accumulation of a bacterial cellulase in Chlamydomonas reinhardtii chloroplasts

“…In this work, we developed transplastomic C. reinhardtii strains that can produce Cel6A, an endoglucanase from T. fusca, which has been previously shown to accumulate variably in tobacco chloroplasts. The high conservation of chloroplasts across microalgae species makes it likely that regulatory strategies successful in C. reinhardtii will be transferrable to related algae with better lipid accumulation traits, such as Chlorella C596 [ 35 ].…”

Eukaryote microbes potential for bioflocs in the swamp aquaculture

“…Chlorella autotrophica or Chlorella sp. is a type of marine Chlorella that can adapt to the freshwater because of its euryhaline capability (Mansfeldt et al, 2016) This type of microalgae can be used as green water on the aquaculture system and live feed for zooplankton and shrimp. Chlorella can be an immune-boosting feed for post shrimp larvae with increased prophenoloxidase Figure 8.…”

Optimization of high quality total RNA isolation from the microalga, Chlorella sp. (Trebouxiophyceae, Chlorophyta) for next‐generation sequencing

“…In contrast, effective lysis is achieved by flash freezing cells with liquid nitrogen followed by mechanical grinding of cells with a mini pestle mixer. An alternative for high yields is to use a bead‐beater (Kim et al ; Mansfeldt et al ). The PureLink RNA mini kit, which uses a spin‐column technology and selective binding properties of silica membranes, did not give satisfactory results.…”

“…Various cell disruption methods have been used for RNA isolation from green microalgae. Bead‐beating (Kim et al ; Mansfeldt et al ) and repeated freeze‐thawing and vortexing (Singh et al ) are some of the techniques used to break rigid cell walls. The lack of standardized unit of measurement for RNA yields (e.g.…”