Insight into the symbiotic lifestyle of DPANN archaea revealed by cultivation and genome analyses.

Decades of culture-independent analyses have resulted in proposals of many tentative archaeal phyla with no cultivable representative. Members of DPANN (an acronym of the names of the first included phyla Diapherotrites, Parvarchaeota, Aenigmarchaeota, Nanohaloarchaeota, and Nanoarchaeota), an archaeal superphylum composed of at least 10 of these tentative phyla, are generally considered obligate symbionts dependent on other microorganisms. While many draft/complete genome sequences of DPANN archaea are available and their biological functions have been considerably predicted, only a few examples of their successful laboratory cultivation have been reported, limiting our knowledge of their symbiotic lifestyles. Here, we investigated physiology, morphology, and host specificity of an archaeon of the phylum "Candidatus Micrarchaeota" (ARM-1) belonging to the DPANN superphylum by cultivation. We constructed a stable coculture system composed of ARM-1 and its original host Metallosphaera sp. AS-7 belonging to the order Sulfolobales Further host-switching experiments confirmed that ARM-1 grew on five different archaeal species from three genera-Metallosphaera, Acidianus, and Saccharolobus-originating from geologically distinct hot, acidic environments. The results suggested the existence of DPANN archaea that can grow by relying on a range of hosts. Genomic analyses showed inferred metabolic capabilities, common/unique genetic contents of ARM-1 among cultivated micrarchaeal representatives, and the possibility of horizontal gene transfer between ARM-1 and members of the order Sulfolobales Our report sheds light on the symbiotic lifestyles of DPANN archaea and will contribute to the elucidation of their biological/ecological functions.

Sulfurisphaera javensis sp. nov., a hyperthermophilic and acidophilic archaeon isolated from Indonesian hot spring, and reclassification of Sulfolobus tokodaii Suzuki et al. 2002 as Sulfurisphaera tokodaii comb. nov.

A novel hyperthermophilic, acidophilic and facultatively anaerobic archaeon, strain KD-1T, was isolated from an acidic hot spring in Indonesia and characterized with the phylogenetically related species Sulfurisphaera ohwakuensis Kurosawa et al. 1998, Sulfolobus tokodaii Suzuki et al., 2002 and Sulfolobus yangmingensis Jan et al. 1999. Cells of KD-1T were irregular cocci with diameters of 0.9-1.3 µm. The strain grew at 60-90 °C (optimum 80-85 °C), pH 2.5-6.0 (optimum pH 3.5-4.0) and 0-1.0 % (w/v) NaCl concentration. KD-1T grew anaerobically in the presence of S0 (headspace: H2/CO2) and FeCl3 (headspace: N2). Under aerobic conditions, chemolithoautotrophic growth occurred on S0, pyrite, K2S4O6, Na2S2O3 and H2. This strain utilized various complex substrates, such as yeast extract, but did not grow on sugars and amino acids as the sole carbon source. The main core lipids were calditoglycerocaldarchaeol and caldarchaeol. The DNA G+C content was 30.6 mol%. Analyses of phylogenetic trees based on 16S rRNA and 23S rRNA genes indicated that KD-1T formed an independent lineage near Sulfurisphaera ohwakuensis TA-1T, Sulfolobus tokodaii 7T and Sulfolobus yangmingensis YM1T. On the basis of the results of morphological, physiological, chemotaxonomic and phylogenetic analyses, KD-1T represents a novel species of the genus Sulfurisphaera Kurosawa et al. 1998, for which the name Sulfurisphaera javensis sp. nov. is proposed. The type strain is KD-1T (=JCM 32117T=InaCC Ar81T). Based on the data, we also propose the reclassification of Sulfolobus tokodaii Suzuki et al., 2002 as Sulfurisphaera tokodaii comb. nov. (type strain 7T=JCM 10545T=DSM 16993T).

Cloning and characterization of an acidic lipase from a lipolytic bacterium in tempeh.

BACKGROUND: Lipases have emerged as essential biocatalysts, having the ability to contribute to a wide range of industrial applications. Microbial lipases have garnered significant industrial attention due to their stability, selectivity, and broad substrate specificity. In the previous study, a unique lipolytic bacterium (Micrococcus luteus EMP48-D) was isolated from tempeh. It turns out the bacteria produce an acidic lipase, which is important in biodiesel production. Our main objectives were to clone the acidic lipase and investigate its potential in biodiesel production. RESULT: In this study, the gene encoding a lipase from M. luteus EMP48-D was cloned and expressed heterologously in Escherichia coli. To our knowledge, this is the first attempt at the cloning and expression of the lipase gene from Micrococcus luteus. The amino acid sequence was deduced from the nucleotide sequence (1356 bp) corresponded to a protein of 451 amino acid residues with a molecular weight of about 40 kDa. The presence of a signal peptide suggested that the protein was extracellular. A sequence analysis revealed that the protein had a lipase-specific Gly-X-Ser-X-Gly motif. The enzyme was identified as an acidic lipase with a pH preference of 5.0. Fatty acid preferences for enzyme activities were C8 and C12 (p-nitrophenyl esters), with optimum temperatures at 30-40 °C and still remaining active at 80°C. The enzyme was also shown to convert up to 70% of the substrate into fatty acid methyl ester. CONCLUSION: The enzyme was a novel acidic lipase that demonstrated both hydrolytic and transesterification reactions. It appeared particularly promising for the synthesis of biodiesel as this enzyme's catalytic reaction was optimum at low temperatures and was still active at high temperatures.