Co-culturing bacteria and microalgae in organic carbon containing medium

Area of Science:

• Microbiology
• Marine Biology
• Biotechnology

Background:

• Microalgae and bacteria form symbiotic relationships in natural and lab settings.
• Bacteria provide microalgae with essential nutrients like carbon dioxide and vitamins.
• Previous co-cultures were limited to photoautotrophic conditions, resulting in low cell densities.

Purpose of the Study:

• To investigate the feasibility of co-culturing bacteria and microalgae under mixotrophic conditions.
• To assess the impact of mixotrophic co-culturing on microalgal growth and bacterial populations.
• To determine the effectiveness of this strategy for enhancing microalgal cultivation.

Main Methods:

• Isolation and identification of bacteria associated with microalgae using 16S rRNA gene sequencing.
• Co-culturing selected bacterial strains (Muricauda sp.) with axenic microalgae (Tetraselmis chuii, Cylindrotheca fusiformis, Nannochloropsis gaditana) in a medium supplemented with organic carbon.
• Monitoring cell densities of both microalgae and bacteria over a 33-day period.

Main Results:

• Co-culturing significantly increased the cell density of Tetraselmis chuii (21.37-31.18%) and Cylindrotheca fusiformis (65.42-83.47%).
• Nannochloropsis gaditana growth was inhibited under mixotrophic co-culture conditions.
• Bacterial populations initially decreased then stabilized with Cylindrotheca fusiformis, but declined with Tetraselmis chuii and Nannochloropsis gaditana.

Conclusions:

• Microalgae-bacteria co-cultures under mixotrophic conditions represent a highly effective strategy for enhancing microalgal cultivation.
• The success of mixotrophic co-culturing is species-specific, with some microalgae benefiting more than others.
• Further research can optimize these co-culture systems for specific applications.