# Unanticipated similarities and expected differences in the taxonomic composition and potential toxicity of cyanobacteria in biological soil crusts across hot and cold deserts

## TL;DR

This study compares cyanobacteria in soil crusts from two deserts and finds similar core bacteria but differences in specific families and potential toxicity.

## Contribution

The study reveals unexpected similarities in cyanobacterial composition and identifies toxin-related genes in biocrusts from geographically distinct deserts.

## Key findings

- Core bacterial phyla like Pseudomonadota and Cyanobacteriota are similar in both deserts.
- Cyanobacterial families differ, with Nostocaceae and Nodosilineaceae dominating in Pamir.
- Cyanotoxin-producing species and genes like mcyE and ndaF are present in both deserts.

## Abstract

The hot deserts of California and the cool, mountainous deserts of the Eastern Pamir region are geographically and climatically distinct, yet they share a common feature. Their arid soils host pioneering microorganisms that form biological soil crusts (BSCs), one of the earliest forms of life in this biome. This study aimed to reveal and compare the taxonomic composition, structure, and potential toxicity of cyanobacteria in these distant deserts, using simultaneous analysis. We observed significant differences in soil chemical properties, with higher average electrical conductivity in California and higher median levels of iron, nitrogen, carbon, magnesium, sodium, potassium, and calcium in Pamir. Despite this, the taxonomic composition and structure of the core bacteria phyla were similar, with Pseudomonadota, Actinomycetota, Bacteroidota, and Cyanobacteriota dominating in both locations. However, at the family level, bacterial communities showed more variability. Within Cyanobacteriota, the most abundant groups in California’s biocrust samples were unidentified families, followed by Nostocaceae, Coleofasciculaceae, Chroococcidiopsidaceae, and Phormidiaceae. In Pamir, Nodosilineaceae and Nostocaceae dominated, with a lower contribution from unknown families. In samples from both deserts, we identified cyanobacterial species known to produce cyanotoxins, along with the genes mcyE + ndaF and mcyD, which are responsible for the microcystin and nodularin biosynthesis pathways.

Flowchart illustrating the process for exosome-based miRNA diagnostics in lung adenocarcinoma (LUAD). Serum is processed through ultracentrifugation or GlyExo-Capture, using magnetic beads, to isolate exosomes within varying times. Exosomes undergo small RNA sequencing, followed by RT-qPCR in different study groups: screening, training, and validation sets. The flow includes selecting WGA-exosomal miRNAs, establishing, and verifying a 4-miRNA panel's diagnostic performance. Images of people and lab equipment accompany each stage.