Cross-kingdom metagenomic profiling of Lake Hillier reveals pigment-rich polyextremophiles and wide-ranging metabolic adaptations

Background Lake Hillier is a hypersaline lake known for its distinctive bright pink color. The cause of this phenomenon in other hypersaline sites has been attributed to halophiles, Dunaliella , and Salinibacter , however, a systematic analysis of the microbial communities, their functional features, and the prevalence of pigment-producing-metabolisms has not been previously studied. Our results are evidence that Lake Hillier is composed of a diverse set of microorganisms including archaea, bacteria, algae, and viruses. Our data indicate a core microbiome in Lake Hillier composed of multiple pigment-producer microbes, many of which are cataloged as polyextremophiles. Additionally, we estimated the diversity of metabolic pathways in the lake and determined that many of these are related to pigment production. We reconstructed complete or partial genomes for 21 discrete bacteria (N = 14) and archaea (N = 7), only 2 of which could be taxonomically annotated to previously observed species. Our findings provide the first metagenomic study to decipher the source of the pink color of Australia’s Lake Hillier. The study of this pink hypersaline environment is evidence of a microbial consortium of pigment producers, a repertoire of polyextremophiles, a core microbiome and potentially novel species. ### Competing Interest Statement The authors have declared no competing interest. * XMP : Extreme Microbiome Project AGRF : Australian Genome Research Facility WGS : Whole Genome Sequencing TMD : The Microbe Directory GTDB : Genome Taxonomy Database PSB : Purple sulfur-bacteria NPSN : Purple non-sulfur-bacteria MAGs : Metagenome-Assembled Genomes ANI : Average Nucleotide Identity BGCs : Biosynthetic Gene Clusters GCF : Gene Cluster Family