Donoso, G. | bioRxiv Science

bioRxiv2024

Rhizospheric bacteria from the Atacama Desert hyper-arid core: cultured community dynamics and plant growth promotion

The Atacama Desert is the oldest and driest desert on Earth, with environmental conditions including great temperature variations, high UV-radiation, drought, high salinity, making it a natural laboratory to study the limits of life and resistance strategies. However, it shows great biodiversity harboring vast forms of adapted life and can be used as a model of desertification processes. While desertification is increasing as result of climate change and human activities, is necessary to optimize soil and water usage, where stress-resistant crops are possible solutions. As many studies have revealed the great impact of rhizobiome over plant growth efficiency and resistance to abiotic stress, we set up to explore the rhizospheric soils of Suaeda foliosa and Distichlis spicata from the Atacama Desert. By culturing these soils and using 16S rRNA amplicon sequencing, we address the community taxonomy composition dynamics, the stability through time and the ability to promote lettuce plants growth. The rhizospheric soil communities were dominated by the families Pseudomonadaceae, Bacillaceae and Planococcaceae for S. foliosa and Porphyromonadaceae and Haloferacaceae for D. spicata. Nonetheless, the cultures were completely dominated by the Enterobacteriaceae family (up to 98%). Effectively, lettuce plants supplemented with the cultures showed greater size and biomass accumulation, we identify 12 candidates that could be responsible of these outcomes, of which 5 (Enterococcus, Pseudomonas, Klebsiella, Paenisporosarcina and Ammoniphilus) were part of the built co-occurrence network, being Klebsiella a major participant. We aim to contribute to the efforts to characterize the microbial communities as key for the plants survival in extreme environments, and as a possible source of consortia with plant growth promotion traits aiming agricultural applications. IMPORTANCEThe current scenario of climate change and desertification represents a series of incoming challenges for all living organisms, also as the human population grows rapidly, so is rising the demand for food and natural resources; thus, it is necessary to make agriculture more efficient by optimizing soil and water usages thus ensuring future food supplies. Particularly, the Atacama Desert (northern Chile) is considered the most arid place on Earth as a consequence of geological and climatic characteristics, such as the naturally low precipitation patterns and high temperatures, which makes it an ideal place to carry out research that seeks to aid agriculture to the future sceneries, which are predicted to resemble these. The use of microorganism consortia from plants thriving under these extreme conditions to promote plant growth, improve crops and make "unsuitable" soils farmable is our main interest. TWEETCultures of rhizospheric soils from Atacama Desert resilient plants were enriched in Klebsiella, Bacillus and Brevibacillus which promoted lettuce growth

microbiology↗

bioRxiv2022

First detection of Leptospira santarosai in the reproductive track of a boar: a potential threat to swine production and public health

BackgroundLeptospirosis causes significant economic losses and is an occupational risk in the swine industry, especially in developing tropical regions where social and geoclimatic conditions are favorable for the transmission of this disease. Although vaccination can reduce infection risk, efficacy is diminished if local genetic and antigenic variants of the pathogen are not accounted for in the vaccine. Identifying and characterizing strains that circulate in different populations is therefore critical for public health mitigation practices. Methodology/Principal findingsOur study was conducted on a rural breeding farm in Ecuador, where we identified, for the first time, Leptospira santarosai in the kidneys, testicles, and ejaculate of a vaccinated boar. L. santarosai was detected with a PCR assay that targets lipL32, and identified by target MLST gene sequencing using an Oxford Nanopore MinION sequencer. Conclusions/SignificanceAs L. santarosai is pathogenic in other livestock species and humans, our finding highlights the need to evaluate the prevalence and epidemiological significance of this pathogen in pigs. In addition, further studies are needed to identify and characterize local serovars that may impact diagnosis and vaccination programs to better control leptospirosis in pigs and spillover into the human population. Author summaryLeptospirosis poses a significant threat to human and animal health. In tropical countries, leptospirosis is very common, and responsible of economic losses in the livestock industry. In peridomestic and rural farms, the spillover of leptospira to humans is particularly likely as humans live and work in close proximity to animals. Although animal vaccination can reduce risk of infection, efficacy is diminished when local variants are not included in the vaccine. This report describes, for the first time, the presence of Leptospira santarosai in the reproductive tract of a vaccinated domestic boar from a rural farm in Ecuador. We detected the pathogen in its semen and urine, and despite no tissue damage, was observed in the kidneys, testes or epididymis. The farm veterinarian reported reproductive problems in sows inseminated with the semen from this boar. Our results highlight the importance of recognizing locally circulating serovars and species so that they can be included in vaccines to prevent infection and disease. Effective control of leptospirosis in livestock not only reduces economic losses for breeders, but also reduces the risk of infection and disease in humans.

microbiology↗