Insights into the Lysine Acetylome of the Haloarchaeon during Oxidative Stress by Quantitative SILAC-Based Proteomics.

Oxidative stress adaptation strategies are important to cell function and are linked to cardiac, neurodegenerative disease, and cancer. Representatives of the domain are used as model organisms based on their extreme tolerance to oxidants and close evolutionary relationship with eukaryotes. A study of the halophilic archaeon reveals lysine acetylation to be associated with oxidative stress responses.

Quantitative Mass Spectrometry by SILAC in Haloferax volcanii.

The development of mass spectrometry (MS)-based proteomics methods has been critical in providing new insight about cellular processes and adaptations in all domains of life. While traditional MS-based methods are not inherently quantitative, technologies are now available to overcome this limitation. Of note, stable isotope labeling of amino acids in cell culture (SILAC) is reported as a reliable tool to label proteomes for quantitative MS-based proteomics that is accurate and flexible for multiplexing.

TrmB Family Transcription Factor as a Thiol-Based Regulator of Oxidative Stress Response.

Oxidative stress causes cellular damage, including DNA mutations, protein dysfunction, and loss of membrane integrity. Here, we discovered that a TrmB (transcription regulator of operon) family protein (Pfam PF01978) composed of a single winged-helix DNA binding domain (InterPro IPR002831) can function as thiol-based transcriptional regulator of oxidative stress response. Using the archaeon Haloferax volcanii as a model system, we demonstrate that the TrmB-like OxsR is important for recovery of cells from hypochlorite stress.

Expression and tandem affinity purification of 20S proteasomes and other multisubunit complexes in Haloferax volcanii.

Tandem affinity purification is a useful strategy to isolate multisubunit complexes of high yield and purity but can be limited when working with halophilic proteins that are not properly expressed in Escherichia coli. Halophilic proteins are desirable for bioindustrial applications as they are often stable and active in organic solvents; however, these proteins can be difficult to express, fold, and purify by traditional technologies. Haloarchaea provide a useful alternative for expression of halophilic proteins.

High-level synthesis and secretion of laccase, a metalloenzyme biocatalyst, by the halophilic archaeon Haloferax volcanii.

Haloarchaea and their enzymes have extremophilic properties desirable for use as platform organisms and biocatalysts in the bioindustry. These GRAS (generally regarded as safe) designated microbes thrive in hypersaline environments and use a salt-in strategy to maintain osmotic homeostasis. This unusual strategy has resulted in the evolution of most of the intracellular and extracellular enzymes of haloarchaea to be active and stable not only in high salt (2-5M) but also in low salt (0.

Bacterial-like nitric oxide synthase in the haloalkaliphilic archaeon Natronomonas pharaonis.

Bacterial nitric oxide (NO) synthases (bNOS) play diverse and important roles in microbial physiology, stress resistance, and virulence. Although bacterial and mammalian NOS enzymes have been well-characterized, comparatively little is known about the prevalence and function of NOS enzymes in Archaea. Analysis of archaeal genomes revealed that highly conserved bNOS homologs were restricted to members of the Halobacteria.

Temporal Analysis of the Microbial Community from the Crystallizer Ponds in Cabo Rojo, Puerto Rico, Using Metagenomics.

The Cabo Rojo solar salterns are a hypersaline environment located in a tropical climate, where conditions remain stable throughout the year. These conditions can favor the establishment of steady microbial communities. Little is known about the microbial composition that thrives in hypersaline environments in the tropics.