Effect of Bacillus spp. on Lettuce Growth and Root Associated Bacterial Community in a Small-Scale Aquaponics System
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Date
2021
Journal Title
Journal ISSN
Volume Title
Publisher
Agronomy
Abstract
The integration of probiotics in aquaponics systems is a strategy for mitigating environmental
impacts and for promoting sustainable agriculture. In order to understand the role of probiotics,
we investigated the effect of a commercial probiotic mixture of Bacillus subtilis and B. licheniformis on
the growth of lettuce (Lactuca sativa L.) under deep-water culture integrated with Mozambique tilapia
(Oreochromis mossambicus). We determined plant growth, water quality parameters, and leaf mineral
analysis, and assessed the influence of a probiotic mixture on the microbiota. Bacterial communities
were analyzed by high-throughput 16S rRNA gene sequencing. Compared to the control systems, the
addition of the probiotic Bacillus significantly increased the concentration of nitrate and phosphate in
deep water culture solution, which contributed to improved lettuce growth. In both the growth trials,
the Fv/Fm, the mean shoot dry weight, and the mean fresh weight of the harvested shoots from
the Bacillus treatment were significantly higher than those observed for the control plants. Higher
concentrations of phosphorus, potassium, and zinc in the lettuce leaves were found in systems
that received the Bacillus. Although differences were observed at the phylum level, Proteobacteria
and Bacteroidetes were predominant in both the Bacillus-treatment and the control systems. At the
genus level, however, the communities present in the two types of systems were heterogeneous
with Bacillus-treated systems, containing significantly higher numbers of Chryseobacterium, Bacillus,
Nitrospira, Polynucleobacter, and Thermomonas. The results indicate that Bacillus supplementation can
effectively alleviate nutrient deficiencies, improve water quality, and modify the composition of
bacterial communities in aquaponics systems.
Description
Keywords
aquaponics, lettuce, plant growth, probiotics, Mozambique tilapia
Citation
Kasozi, N.; Kaiser, H.; Wilhelmi, B. Effect of Bacillus spp. on Lettuce Growth and Root Associated Bacterial Community in a Small-Scale Aquaponics System. Agronomy 2021, 11, 947. https://doi.org/10.3390/ agronomy11050947