Browsing by Author "Kaiser, Horst"

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    The complex microbiome in aquaponics: significance of the bacterial ecosystem
    (Annals of Microbiology, 2021) Kasozi, Nasser; Abraham, Benjamin; Kaiser, Horst; Wilhelmi, Brendan
    Aquaponics is a technology that has minimal impact on the environment and which is often promoted as a solution for sustainable food production. Developing aquaponics sustainably requires a thorough understanding of the biological components of the system. Recent reports on the bacterial populations of aquaponics systems using new DNA sequencing technologies are revealing a complex and diverse microbial ecosystem. The purpose of this review is to present information on microbial composition and various factors affecting bacterial activity in aquaponics systems. Approaches for establishing a bacterial ecosystem during the setup of an aquaponics system, and microbiological safety of aquaponics products are also highlighted. Methods: This review was developed by evaluating and synthesising current literature of peer-reviewed publications related to aquaponics and microbial communities. Based on the results from credible academic journals, publications were categorised into five groups: methods used to characterise microbiomes, biofiltration microorganisms, bacterial diversity, biofilter establishment, and safety of aquaponics products. Results: The microbial ecosystem is essential for biological filtration of water through the mineralisation of nutrients required for plant growth in an integrated system. The aquaponics microbiome is complex, and bacterial composition varies between the different compartments of these systems. Establishing these bacterial ecosystems is essential for optimal functioning of aquaponics. At the phylum level, Proteobacteria and Bacteroidetes are dominant in aquaponics systems. Despite bacteria being fundamental to aquaponics, there are currently no reports of human pathogens in aquaponics products.
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    Effect of Bacillus spp. on Lettuce Growth and Root Associated Bacterial Community in a Small-Scale Aquaponics System
    (Agronomy, 2021) Kasozi, Nasser; Kaiser, Horst; Wilhelmi, Brendan
    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.
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    Iron supplementation and management in aquaponic systems: A review
    (Aquaculture Reports, 2019) Kasozi, Nasser; Tandlich, Roman; Fick, Martin; Kaiser, Horst; Wilhelmi, Brendan
    Iron is one of the essential micronutrients for plant development and fish growth in aquaponic systems. Iron is an essential element for photosynthesis, DNA synthesis, and many other cellular functions for plants. With regard to fish, it is an integral component of proteins involved in cellular respiration and oxygen transfer. Aquaponic systems are often iron deficient due to low amounts of iron in commercial fish feeds. Therefore, iron needs to be supplemented to ensure optimal plant performance. Adding these supplements requires close management of the system, and careful selection of chelating substances as the Fe-chelate bioavailability is environment dependent. Reports of iron supplementation and management in aquaponic systems are limited. This review critically examines iron supplementation strategies, different sources of iron and factors influencing iron uptake for optimal biomass production. The effectiveness of different iron chelates is also discussed. Furthermore, optimum ranges of dissolved iron concentrations for different components in an aquaponic system are reported. This review aims to provide a better understanding of iron optimisation strategies to minimise iron deficiency and enhance biomass growth.
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    Metabarcoding Analysis of Bacterial Communities Associated with Media Grow Bed Zones in an Aquaponic System
    (International journal of microbiology, 2020) Kasozi, Nasser; Kaiser, Horst; Wilhelmi, Brendan
    )e development of environmentally sustainable plant and fish production in aquaponic systems requires a complete understanding of the systems’ biological components. In order to better understand the role of microorganisms in this association, we studied the bacterial communities in the dry, root, and mineralized zones of a flood-and-drain media bed aquaponic system. Bacterial communities were characterized using metabarcoding of the V3-V4 16S rRNA regions obtained from paired-end Illumina MiSeq reads. Proteobacteria, Actinobacteria, and Bacteroidetes accounted for more than 90% of the total community in the dry zone and the effluent water. )ese phyla also accounted for more than 68% of the total community in the root and mineralized zones. )e genera Massilia, Mucilaginibacter, Mizugakiibacter, and Rhodoluna were most dominant in the dry, root, and mineralized zones and in the effluent water, respectively. )e number of shared operational taxonomic units (OTUs) for the three zones was 241, representing 7.15% of the total observed OTUs. )e number of unique OTUs in samples from dry zone, root zone, mineralized zone, and effluent water was 485, 638, 445, and 383, respectively.)e samples from the root zone harbored more diverse communities than either the dry or mineralized zones. )is study is the first to report on the bacterial community within the zones of a flood-and-drain media bed. )us, this information will potentially accelerate studies on other microbial communities involved in the bioconversion of nitrogen compounds and mineralization within these types of aquaponic systems.