![]() The majority of the species isolated from the phylum Planctomycetes are from the class, Planctomycetia - a class that consists of four orders: Planctomycetales, Pirellulales, Gemmatales, and Isosphaerales ( Dedysh et al., 2020). Candidatus Brocadiae is considered a third class within the phylum Planctomycetes, although pure cultures are not yet available for its members and its class-level status remains to be defined ( Kartal et al., 2012 Kartal et al., 2013). Currently, all taxonomically described Planctomycetes with validly published names can be divided into two recognized classes: Planctomycetia and Phycisphaerae ( Fukunaga et al., 2009 Wiegand et al., 2018). Although Planctomycetes bacteria are highly abundant in nature, relatively few have been cultivated therefore, the unexplored groups lack cultured and characterized representatives ( Fuerst and Sagulenko, 2011). Planctomycetes bacteria are ubiquitous in many environments, including lakes ( Pollet et al., 2011), wetlands ( Dedysh and Ivanova, 2019), soil ( Buckley et al., 2006), freshwater ( Brümmer et al., 2004), oceanic waters, and abyssal sediments ( Woebken et al., 2007 Goffredi and Orphan, 2010), where they are critical for carbon and nitrogen cycling although, the specific pathways used are unknown ( Wiegand et al., 2018). The work will be of interest to bacteriologists and microbiologists in general. The study uses convincing evidence, based on experiments using growth assays, phylogenetics, transcriptomics, and gene expression data. This important study advances the understanding of physiological mechanisms in deep-sea Planctomycetes bacteria, revealing unique characteristics such as the only known Phycisphaerae using a budding mode of division, extensive involvement in nitrate assimilation and release phage particles without cell death. ![]() Overall, these findings expand our understanding of deep-sea Planctomycetes bacteria, while highlighting their ability to metabolize nitrogen when reprogrammed by chronic viruses. This bacteriophage then enabled strain ZRK32, and another marine bacterium that we studied, to metabolize nitrogen through the function of auxiliary metabolic genes (AMGs). Moreover, supplementation with NO 3 - or NH 4 + induced strain ZRK32 to release a bacteriophage in a chronic manner, without host cell lysis. Based on the combined results from growth assays and transcriptomic analyses, we found that rich nutrients, or supplementation with NO 3 - or NH 4 + promoted the growth of strain ZRK32 by facilitating energy production through the tricarboxylic acid (TCA) cycle and the Embden–Meyerhof–Parnas (EMP) glycolysis pathway. We show that strain ZRK32 replicates using a budding mode of division. ![]() ![]() Our genomic, physiological and phylogenetic analyses indicate that strain ZRK32 is a novel species, which we propose be named: Poriferisphaera heterotrophicis. Here, we have successfully cultured a novel strain of Planctomycetes (strain ZRK32) from a cold seep sediment, by using an enriched medium supplemented with rifampicin and different sources of nitrogen. However, few deep-sea Planctomycetes members have been cultivated, limiting our understanding of Planctomycetes in the deep biosphere. Planctomycetes bacteria are ubiquitously distributed across various biospheres and play key roles in global element cycles.
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