Symbiotic association in Chlorella culture

Abstract

Chlorella sorokiniana IAM C-212 has long been maintained in slant culture as a mixed strain, representing an associated natural microbial consortium. In this study, the consortium was separated and five nonalgal constituents, a fungal strain (CSSF-1), and four bacterial strains (CSSB-1, CSSB-2, CSSB-3, and CSSB-4) were isolated and identified. 16S rDNA sequence analysis revealed that strains CSSB-1, CSSB-2, CSSB-3, and CSSB-4 were close to Ralstonia pickettii (99.8% identity), Sphingomonas sp. DD38 (99.4% identity), Microbacterium trichotecenolyticum (98.6% identity), and Micrococcus luteus (98.6% identity) respectively. 18S rDNA sequence analysis revealed that strain CSSF-1 resembled Acremonium-like hyphomycete KR21-2 (98.8%). The fungal strain CSSF-1 and one of the bacterial strains, CSSB-3, were found to promote the growth of Chlorella while the presence of bacterial strains CSSB-1 and CSSB-2 had no effect. Strain CSSB-4 could not be subcultured so its role was not elucidated. These results show that the interaction between Chlorella and its symbionts under photoautotrophic conditions involved both mutualism and commensalisms. The chlorophyll content of mixed strain was stable in long-term cultivation (7 months) while the chlorophyll content of a pure culture showed a marked decline. Electron microscopic analysis showed the two bacterial strains CSSB-2 and CSSB-3 were harbored on the sheath excreted by Chlorella, while the fungal strain CSSF-1 and the bacterial strain CSSB-1 directly adhered to the Chlorella cell surface. This report is the first observation of a symbiotic relationship among fungus, bacteria, and Chlorella, and the first observation of direct adhesion of fungus and bacteria to Chlorella in a consortium.

Effect of Bacterial-algal Biostimulant on the Yield and Internal Quality of Lettuce (Lactuca sativa L.) Produced for Spring and Summer Crop

“…produces auxins (Yin et al, 2015), which support the root system of plants (Takahashi, 2013), and extracellular phosphatases (Pfeiffer, 1996), which exposes phosphorus to plants (Lee, 1988); Chlorella vulgaris helps to start initial bacterial growth (Cole, 1982;Watanabe et al, 2005); Azotobacter sp. produces extracellular biopolymers (Remminghorst and Rehm, 2006), which are necessary for aquaretence capacity cover Redmile-Gordon et al, 2015); while Azotobacter sp.…”

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

“…In a study of the long-term association of microbes with a Chlorella culture, four bacterial species and a fungus were found to be harbored on the sheath of the Chlorella or directly attached to the Chlorella cell surface. Interestingly, the chlorophyll content of the Chlorella together with these symbionts was maintained at a high level for seven months whereas the chlorophyll content of the axenic Chlorella declined markedly (Watanabe et al, 2005). In a study of the bacteria associated with three microalgae, Chlorella saccharophila, Ulothrix variabilis and Volvox aureus, many of the bacteria were Alpha-, Beta-and Gamma-proteobacteria.…”

Presence of previously undescribed bacterial taxa in non-axenic Chlorella cultures

“…There are some reports on the relationship between bacteria and aquatic microalgae in such cultures. Watanabe et al (2005) isolated one strain each of four bacterial species and one fungal species from a non-axenic culture of Chlorella sorokiniana (Chlorophyceae, Chlorophyta), and detected a growthpromoting effect of a bacterial and the fungal strain on the alga. A symbiotic relationship between bacteria and microalgae in artificial media has also been reported.…”