Organic solvent tolerance of halophilic α-amylase from a Haloarchaeon, Haloarcula sp. strain S-1

A halophilic archaeon, Haloarcula sp. strain S-1, produced extracellular organic solvent-tolerant -amylase. Molecular mass of the enzyme was estimated to be 70 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This amylase exhibited maximal activity at 50°C in buffer containing 4.3 M NaCl, pH 7.0. Moreover, the enzyme was active and stable in various organic solvents (benzene, toluene, and chloroform, etc.). Activity was not detected at low ionic strengths, but it was detected in the presence of chloroform at low salt concentrations. On the other hand, no activity was detected in the presence of ethyl alcohol and acetone.     

Molecular characterization of the group II chaperonin from the hyperthermophilic archaeum Pyrococcus horikoshii OT3

The group II chaperonin from the hyperthermophilic archaeum Pyrococcus horikoshii OT3 (PhCPN) and its functional cooperation with the cognate prefoldin were investigated. PhCPN existed as a homo-oligomer in a double-ring structure, which protected the citrate synthase of a porcine heart from thermal aggregation at 45°C, and did the same on the isopropylmalate dehydrogenase (IPMDH) of a thermophilic bacterium, Thermus thermophilus HB8, at 90°C. PhCPN also enhanced the refolding of green fluorescent protein (GFP), which had been unfolded by low pH, in an ATP-dependent manner. Unexpectedly, functional cooperation between PhCPN and Pyrococcus prefoldin (PhPFD) in the refolding of GFP was not observed. Instead, cooperation between PhCPN and PhPFD was observed in the refolding of IPMDH unfolded with guanidine hydrochloride. Although PhCPN alone was not effective in the refolding of IPMDH, the refolding efficiency was enhanced by the cooperation of PhCPN with PhPFD.     

Isolation and Phylogenetic Analysis of Halophilic Archaeon AJ6

Halophilic archaeon A J6 was isolated and purified from the Altun Mountain National Nature Reserve of the Xinjiang Uygur Autonomous Region.Strain AJ6 is a Gram-negative rod whose size is 0.2-0.6 by 1.6-4.2 μm,wherein a few cells are globular.The optimum salt concentration for its growth is 20% NaC1 and 0.6% Mg2+,and the optimum pH is 6.0-7.0.Morphological,physiological,and biochemical characteristics of strain AJ6 were observed.The 16S rRNA encoding gene (16S rDNA)sequence of strain A J6 was amplified by PCR,and its nucteotide sequence was determined subsequently."Clustalw"and"PHYLIP"software bags were used to analyze the 16S rDNA sequence;the homology was compared,and then the phylogenetic tree was established.The results indicate that strain AJ6 is a novel species of the genus Natrinema.The GenBank accession number of the 16S rDNA sequences of strain AJ6 is AY277584.     

The Evolution Pathway of Ammonia-Oxidizing Archaea Shaped by Major Geological Events

Primordial nitrification processes have been studied extensively using geochemical approaches, but the biological origination of nitrification remains unclear. Ammonia-oxidizing archaea (AOA) are widely distributed nitrifiers and implement the rate-limiting step in nitrification. They are hypothesized to have been important players in the global nitrogen cycle in Earth’s early history. We performed systematic phylogenomic and marker gene analyses to elucidate the diversification timeline of AOA evolution. Our results suggested that the AOA ancestor experienced terrestrial geothermal environments at ∼1,165 Ma (1,928–880 Ma), and gradually evolved into mesophilic soil at ∼652 Ma (767–554 Ma) before diversifying into marine settings at ∼509 Ma (629–412 Ma) and later into shallow and deep oceans, respectively. Corroborated by geochemical evidence and modeling, the timing of key diversification nodes can be linked to the global magmatism and glaciation associated with the assembly and breakup of the supercontinent Rodinia, and the later oxygenation of the deep ocean. Results of this integrated study shed light on the geological forces that may have shaped the evolutionary pathways of the AOA, which played an important role in the ancient global nitrogen cycle.     

Crystal structure of an archaeal actin homolog

Prokaryotic homologs of the eukaryotic structural protein actin, such as MreB and ParM, have been implicated in determination of bacterial cell shape, and in the segregation of genomic and plasmid DNA. In contrast to these bacterial actin homologs, little is known about the archaeal counterparts. As a first step, we expressed a predicted actin homolog of the thermophilic archaeon Thermoplasma acidophilum, Ta0583, and determined its crystal structure at 2.1A resolution. Ta0583 is expressed as a soluble protein in T.acidophilum and is an active ATPase at physiological temperature. In vitro, Ta0583 forms sheets with spacings resembling the crystal lattice, indicating an inherent propensity to form filamentous structures. The fold of Ta0583 contains the core structure of actin and clearly belongs to the actin/Hsp70 superfamily of ATPases. Ta0583 is approximately equidistant from actin and MreB on the structural level, and combines features from both eubacterial actin homologs, MreB and ParM. The structure of Ta0583 co-crystallized with ADP indicates that the nucleotide binds at the interface between the subdomains of Ta0583 in a manner similar to that of actin. However, the conformation of the nucleotide observed in complex with Ta0583 clearly differs from that in complex with actin, but closely resembles the conformation of ParM-bound nucleotide. On the basis of sequence and structural homology, we suggest that Ta0583 derives from a ParM-like actin homolog that was once encoded by a plasmid and was transferred into a common ancestor of Thermoplasma and Ferroplasma. Intriguingly, both genera are characterized by the lack of a cell wall, and therefore Ta0583 could have a function in cellular organization.     

Development of a thermostable β-glucuronidase-based reporter system for monitoring gene expression in hyperthermophiles

Mesophilic glucuronidases are the most widely used reporters of gene expression in plants, but unsuitable as reporters in (hyper-)thermophiles due their insufficient thermal stability. Here we present the native 66.8 kDa thermostable β-glucuronidase of Sulfolobus solfataricus. The enzyme activity is characterized in a wide temperature range ideal for, but not limited to, in vivo genetic study of hyperthermophiles. As a proof of concept, we demonstrate its use as a reporter of gene expression in Sulfolobus, by monitoring a promoter fusion created with the β-glucuronidase coding gene gusB and a copper-responsive promoter.     

嗜盐古菌噬菌体研究进展

嗜盐古菌噬菌体是噬菌体的一个重要分支,在群体生态学以及生命的起源与进化历程中扮演重要的角色.综述了嗜盐古菌噬菌体的形态多样性、研究方法、起源与进化几方面的研究报道,指出目前研究中存在的问题,对未来研究进行了展望.     

The ATP-dependent proteases and proteolytic complexes involved into intracellular protein degradation

The review characterizes the main enzymatic systems of selective proteolysis responsible for maintenance of intracellular proteome in prokaryotes, eukaryotes and archaea. The features of proteolytic components of the ATP-dependent proteases as well as similarity and diversity of their regulatory components belonging to AAA⁺ ATPases are discussed.     

Nitrification in terrestrial hot springs of Iceland and Kamchatka

Archaea have been detected recently as a major and often dominant component of the microbial communities performing ammonia oxidation in terrestrial and marine environments. In a molecular survey of archaeal ammonia monooxygenase (AMO) genes in terrestrial hot springs of Iceland and Kamchatka, the amoA gene encoding the alpha-subunit of AMO was detected in a total of 14 hot springs out of the 22 investigated. Most of these amoA-positive hot springs had temperatures between 82 and 97 degrees C and pH range between 2.5 and 7. In phylogenetic analyses, these amoA genes formed three independent lineages within the known sequence clusters of marine or soil origin. Furthermore, in situ gross nitrification rates in Icelandic hot springs were estimated by the pool dilution technique directly on site. At temperatures above 80 degrees C, between 56 and 159 mumol NO(3)(-) L(-1) mud per day was produced. Furthermore, addition of ammonium to the hot spring samples before incubation yielded a more than twofold higher potential nitrification rate, indicating that the process was limited by ammonia supply. Our data provide evidence for an active role of archaea in nitrification of hot springs in a wide range of pH values and at a high temperature.