Mammals’ sperm microbiome: current knowledge, challenges, and perspectives on metagenomics of seminal samples

Abstract

Bacterial growth is highly detrimental to sperm quality and functionality. However, during the last few years, using sequencing techniques with a metagenomic approach, it has been possible to deepen the study of bacteria-sperm relationships and describe non-culturable species and synergistic and antagonistic relationships between the different species in mammalian animals. We compile the recent metagenomics studies performed on mammalian semen samples and provide updated evidence to understand the importance of the microbial communities in the results of sperm quality and sperm functionality of males, looking for future perspectives on how these technologies can collaborate in the development of andrological knowledge.

Characterisation of the urinary microbiome of a frog, and the effect of antibiotics on bacterial abundance and sperm viability during refrigerated storage

“…In the present study, the urinary microbiome of an amphibian was characterised for the first time, adopting a metagenomic approach. This approach is increasingly being used over traditional culturing methods because it allows for the identification of a broad spectrum of species, including otherwise underrepresented, difficult-to-culture species (Contreras et al, 2023). The bacterial communities identified within urine samples in the present study were found to contain a diverse array of both gram-negative and gram-positive bacterial species, with 160 unique species identified across 74 families, and 16 phyla.…”

“…Across externally fertilising taxa, including several species of fish and amphibians, sperm may be exposed to cutaneous bacteria, internal bacteria and environmental bacteria, and each provides a potential source of contamination. In addition to sperm becoming contaminated, there is increasing evidence that a dynamic reproductive microbiome may exist within the reproductive tract in a range of species (Comizzoli and Power, 2019;Molina et al, 2021;Contreras et al, 2023). Bacteria present within sperm samples may contain pathogens or other novel bacteria that can disrupt the host-associated microbiomes of other individuals, including both conspecifics and heterospecifics, that may come into contact with them during transport or use in AF (Jani and Briggs, 2014).…”

“…Antibiotics such as these are used as they are classed as broad-spectrum antibiotics, which are effective at controlling the proliferation of both gram-positive and gram-negative bacteria (Ory and Yow, 1963). Previous studies have indicated that a diverse array of bacteria may be present within sperm samples (Andrabi et al, 2016;Contreras et al, 2023), and thus broad-spectrum antibiotics are required. Both sperm motility and viability has been shown to be maintained significantly longer during storage with the addition of antibiotics compared to without in a range of commercially valuable fish (Stoss and Refstie, 1983;Saad et al, 1988;Christensen and Tiersch, 1996;Segovia et al, 2000;Boonthai et al, 2016;Rahimi et al, 2016;Zidni et al, 2023) and invertebrate species (Nimrat et al, 2005(Nimrat et al, , 2022.…”

Unveiling microbiome signature in inner body fluids: comparison between wild and aquarium small-spotted catshark (Scyliorhinus canicula)

“…Understanding microbial signatures of reproductive fluids is an emerging and critical component of wildlife conservation (Comizzoli et al, 2021). Actually, metagenomic study of the reproductive microbiome is being considered a pivotal tool for species conservation, as it will allow the study of evolutionary and adaptive mechanisms that could be involved in the lack of reproductive efficiency and potentially, its intervention could collaborate in the preservation of endangered species (Contreras et al, 2023).…”