Characterization of Batrachochytrium dendrobatidis Inhibiting Bacteria from Amphibian Populations in Costa Rica

Abstract

Global amphibian declines and extinction events are occurring at an unprecedented rate. While several factors are responsible for declines and extinction, the fungal pathogen Batrachochytrium dendrobatidis (Bd) has been cited as a major constituent in these events. While the effects of this chytrid fungus have been shown to cause broad scale population declines and extinctions, certain individuals and relict populations have shown resistance. This resistance has been attributed in part to the cutaneous bacterial microbiome. Here, we present the first study characterizing anti-Bd bacterial isolates from amphibian populations in Costa Rica, including the characterization of two strains of Serratia marcescens presenting strong anti-Bd activity. Transcriptome sequencing was utilized for delineation of shifts in gene expression of the two previously uncharacterized strains of S. marcescens grown in three different treatments comprising Bd, heat-killed Bd, and a no Bd control. These results revealed up- and down-regulation of key genes associated with different metabolic and regulatory pathways. This information will be valuable in continued efforts to develop a bacterial-based approach for amphibian protection as well as providing direction for continued mechanistic inquiries of the bacterial anti-Bd response.

Infection with Batrachochytrium dendrobatidis is common in tropical lowland habitats: Implications for amphibian conservation

“…There are several explanations for these high infection loads without signs of population decline or disease. For example, it is possible that these populations can coexist with Bd because they carry cutaneous bacteria that release anti‐Bd compounds, although none have been detected in individuals of the relict populations of the Golfito robber frog (Madison et al, ) or in a similar critically endangered species ( C. ranoides ) which also catastrophically declined in the 1980s (Puschendorf et al, ; Zumbado‐Ulate, Bolaños, Willink, & Soley‐Guardia, ). Additionally, antimicrobial peptides and immune defenses (innate and adaptive) may play a role in this host–pathogen coexistence (Rollins‐Smith, ; Woodhams et al, ).…”

“…There are several explanations for these high infection loads without signs of population decline or disease. For example, it is possible that these populations can coexist with Bd because they carry cutaneous bacteria that release anti-Bd compounds, although none have been detected in individuals of the relict populations of the Golfito robber frog (Madison et al, 2017) et al, 2016). Alternatively, persistence of these populations could be associated with behavioral adaptations that rapidly clear infection or to local dry conditions that constrain Bd growth allowing susceptible frogs to coexist with low levels of Bd infection (Chaves et al, 2014;Puschendorf et al, 2011).…”

Assessment of Bacterial Communities Associated With the Skin of Costa Rican Amphibians at La Selva Biological Station

“…Skin is especially important for amphibian physiology; it is responsible for the exchange of respiratory gasses and osmoregulation ( Voyles et al, 2009 ). Furthermore, the skin is in continuous exposure to microorganisms in the environment, hence these potentially symbiotic microbes may be involved in different physiological processes and interacting with pathogens such as Bd ( Madison et al, 2017 ). Knowledge of the ecology of bacterial communities associated with amphibians has only a few years of development ( Bletz et al, 2017a ).…”

Evaluation of the Probiotic Potential of Weissella Confusa Isolated From Traditional Fermented Rice

“…(Holt et al 1994). Genomic DNA was extracted from isolated bacterial cultures (Green and Sambrook 2012), and PCR ampli cation of 16S rDNA gene was achieved by 704F (5'-GTAGCGGTGAAATGCGTAGA-3') and 907R (5'-CCGTCAATTCMTTTRAGTTT -3') (Madison et al 2017). Sequencing of 16S rDNA was carried out at Xcelris Labs Limited, Gujrat, India using ABI 3730xl 96 capillary system using Big Dye Terminator v3.1 kit.…”