Culturing algae with bacteria has been explored as a means of promoting algal growth and altering algal biochemical composition. Plant growth promoting bacteria (PGPB) are of particular interest given their ability to produce phytohormones that are bioactive in microalgae. However, many non-plant growth promoting bacteria also promote algal growth. The objective of this study was to test the benefits of a model PGPB versus non-PGPB in a side-by-side study, evaluating improvement in algal growth rates and impacts on biomass composition. Three green microalgae strains were tested with three strains of bacteria: Azospirillum brasilense (a model PGPB), Escherichia coli (a non-PGPB), and Bacillus megaterium (a potential PGPB). A. brasilense produces the auxin phytohormone indole-3-acetic acid. A. brasilense promoted growth in two of the three algae strains by 39–69% but did not promote growth in Chlorella sorokiniana (strain UTEX 2805). E. coli promoted growth in all three algae strains by 16–64%. That the non-PGPB, E. coli, performed as well as the PGPB, A. brasilense, suggests the importance of symbiotic mechanisms that are ubiquitous among many bacteria. One such mechanism, cell-to-cell O₂-CO₂ exchange, may have been important given significant consumption of algal photosynthate by bacteria. B-vitamin exchange is another widespread mechanism of algal-bacterial symbiosis. The riboflavin metabolite, lumichrome, was detected in low concentrations in co-cultures of A. brasilense (0.4–0.6 ng/mL) and E. coli (5.5–13 ng/mL). These concentrations of lumichrome were found to provide small but statistically significant growth benefits for C. sorokiniana UTEX 2805 and Auxenochlorella protothecoides.

已经研究了用细菌培养藻类作为促进藻类生长和改变藻类生化组成的手段。考虑到植物生长促进细菌（PGPB）产生能够在微藻中具有生物活性的植物激素的能力，因此特别受到关注。但是，许多非植物生长促进细菌也促进藻类生长。这项研究的目的是在一项并行研究中测试模型PGPB与非PGPB的优势，评估藻类生长速率的改善及其对生物质组成的影响。用三种细菌菌株测试了三种绿色微藻菌株：巴西细螺旋藻（Azospirillum brasilense）（PGPB型），大肠杆菌（非PGPB）和巨大芽孢杆菌（Bacillus megaterium）（潜在的PGPB）。一。brasilense生产生长素植物激素吲哚-3-乙酸。一。brasilense促进了三种藻类中的两种藻类的生长39-69％，但没有促进sorokiniana小球藻（UTEX 2805株）的生长。Ë。大肠菌在所有三种藻类中促进了16-64％的生长。即非PGPB，E。大肠杆菌，与PGPB和A一样。brasilense，提出了许多细菌中普遍存在的共生机制的重要性。一种这样的机制，细胞间O ₂ -CO ₂由于细菌大量消耗藻类光合产物，因此交换可能很重要。B-维生素交换是藻-细菌共生的另一种普遍机制。在A的共培养物中检测到低浓度的核黄素代谢产物luminchrome 。brasilense（0.4-0.6纳克/毫升）和Ë。大肠菌（5.5-13 ng / mL）。发现这些浓度的发光铬可为C提供小的但统计上显着的生长益处。sorokiniana UTEX 2805和Auxenochlorella protothecoides。