Characteristics and nutrient function of intestinal bacterial communities in black soldier fly (Hermetia illucens L.) larvae in livestock manure conversion

Abstract

The potential utility of black soldier fly larvae (BSFL) to convert animal waste into harvested protein or lipid sources for feeding animal or producing biodiesel provides a new strategy for agricultural waste management. In this study, the taxonomic structure and potential metabolic and nutrient functions of the intestinal bacterial communities of BSFL were investigated in chicken and swine manure conversion systems. Proteobacteria, Firmicutes and Bacteroidetes were the dominant phyla in the BSFL gut in both the swine and chicken manure systems. After the larvae were fed manure, the proportion of Proteobacteria in their gut significantly decreased, while that of Bacteroidetes remarkably increased. Compared with the original intestinal bacterial community, approximately 90 and 109 new genera were observed in the BSFL gut during chicken and swine manure conversion, and at least half of the initial intestinal genera found remained in the gut during manure conversion. This result may be due to the presence of specialized crypts or paunches that promote microbial persistence and bacteria-host interactions. Ten core genera were found in all 21 samples, and the top three phyla among all of the communities in terms of relative abundance were Proteobacteria, Firmicutes and Bacteroidetes. The nutrient elements (OM, TN, TP, TK and CF) of manure may partly affect the succession of gut bacterial communities with one another, while TN and CF are strongly positively correlated with the relative abundance of Providencia. Some bacterial taxa with the reported ability to synthesize amino acids, Rhizobiales, Burkholderia, Bacteroidales, etc., were also observed in the BSFL gut. Functional analysis based on genes showed that intestinal microbes potentially contribute to the nutrition of BSFL and the high-level amino acid metabolism may partly explain the biological mechanisms of protein accumulation in the BSFL body. These results are helpful in understanding the biological mechanisms of high-efficiency nutrient conversion in BSFL associated with intestinal microbes.

Identification of Bacteria in Two Food Waste Black Soldier Fly Larvae Rearing Residues

“…We studied bacterial community dynamics to identify taxa that were more abundant during BSFL rearing and that were absent in the controls (i.e., substrates stored under the same environmental conditions but without larvae). As suggested by previous researchers (Zhao et al, 2017;Ao et al, 2020), we hypothesized that bacteria enriched in the rearing residue contribute to substrate decomposition. This could imply that pure-culture bacteria and/or defined bacterial mixtures comprised of these bacteria from the residue could potentially increase large-scale BSFL rearing.…”

“…Providencia spp., Dysgonomonas spp., Morganella spp., and Proteus spp. present in the BSFL residues, and absent in controls without larvae, are highly abundant in the BSFL guts (Ao et al, 2020;Cifuentes et al, 2020;Klammsteiner et al, 2020;Raimondi et al, 2020). Identification of Dysgonomonas, Providencia, Morganella, and Proteus in the posterior midgut of BSFL suggest that members of these genera may survive gut passage (Bruno et al, 2019).…”

“…Similar to many insects (Douglas, 2009;Engel and Moran, 2013;Lee and Brey, 2013), Dipteran larvae such as those of Drosophila melanogaster (Diptera: Drosophilidae) and Musca domestica (Diptera: Muscidae) engage in complex interactions with their gut microbiota, as these influence larval immunity (Broderick and Lemaitre, 2012) and metabolism (Shin et al, 2016), growth signaling (Storelli et al, 2011), and nutrient provision (Zurek and Nayduch, 2016). Microbiota associated with BSFL may have similar functions (Ao et al, 2020) considering their similar ecological niche and phylogenetic order (Gold et al, 2018;Zhan et al, 2020). Identification and manipulation (e.g., by addition of bacterial mixtures) of microbiota in BSFL rearing is an additional promising approach to increase rearing performance, next to the optimization of substrate nutrient contents and ratios.…”

Isolation and Identification of Dominant Bacteria From Black Soldier Fly Larvae (Hermetia illucens) Envisaging Practical Applications

“…Even though only a minor fraction of a community unveiled by sequencing methods is culturable ( Alain and Querellou, 2009 ; Prakash et al, 2013 ), the bacterial profile found within these culture-independent studies is to some extent comparable to that found via our approach. Overall, these studies reported that the most representative phyla are the Proteobacteria, the Firmicutes, the Bacteroidetes and to a lesser extent the Actinobacteria ( Jeon et al, 2011 ; Zheng et al, 2013 ; Wynants et al, 2018 ; Bruno et al, 2019b ; Jiang et al, 2019 ; Zhan et al, 2019 ; Ao et al, 2020 ; Klammsteiner et al, 2020 ; Liu et al, 2020 , 2021 ; Raimondi et al, 2020 ; Shelomi et al, 2020 ; Galassi et al, 2021 ; Wu et al, 2021 ). In our collection, these four phyla are also represented: the Proteobacteria (66.3%), the Firmicutes (30.2%), the Bacteroidetes (2.9%) and the Actinobacteria (0.6%).…”

“…As a result, the gut microbial dynamics of these larvae are of specific interest to obtain insight in the insect’s physiology, and further, to increase the yield of the rearing or conversion process. In recent years, the literature available on the composition of the BSFL gut microbiota, possibly in relation with its substrate and other rearing factors, increased substantially, with examples of relevant studies including those of Jeon et al (2011) ; Zheng et al (2013) , Wynants et al (2018) ; Jiang et al (2019) , Ao et al (2020) ; Klammsteiner et al (2020) , Liu et al (2020) ; Raimondi et al (2020) and Shelomi et al (2020) . Based on the aforementioned studies, it can be concluded that a set of genera regularly occurs in the larval gut, such as Enterococcus , Providencia , Morganella , and Dysgonomonas , although relative abundances vary among and within studies.…”