Role of a two-component ResD-ResE system in regulating the expression of guanyl-specific ribonuclease genes in Bacilli

Mechanism of nutrient removal enhancement in low carbon/nitrogen wastewater by a novel high-frequency micro-aeration/anoxic (HMOA) mode

In this study, a novel high-frequency micro-aeration/anoxic (HMOA) mode with a high aeration frequency (15 times/h) and short aeration duration (T_aer = 1 h/cycle) was proposed. Compared with continuous aeration modes, the highest nitrogen and phosphorus removal efficiencies were achieved in the sequencing batch reactor (SBR) under HMOA mode when treating wastewater with carbon/nitrogen (C/N) ratios of 4.5 (85% and 97%, respectively) and 3 (77% and 75%, respectively). Metagenomic analysis was utilized to analyse the microbial metabolic mechanism under the HMOA mode. The results showed that under the HMOA mode, the enhanced transduction and metabolism pathways of nitrate, nitrite, oxygen, phosphorus and acetate provided favourable nutritional conditions for the proliferation of denitrifiers and phosphorus accumulating organisms (PAOs), and simultaneously strengthened the survival capacity of nitrifiers under low dissolved oxygen (DO) conditions. In addition, genes involved in carbon metabolism were upregulated by the HMOA mode, which further increased the utility of carbon sources for denitrifier and PAO metabolism. Consequently, the limited carbon source could be fully utilized in nitrogen and phosphorus removal, which improved the efficiency of treating low C/N wastewater. This study proposed a potential aeration mode for microbial metabolism regulation to enhance nutrient removal in biological wastewater treatment processes.

Phylogenetic distribution of extracellular guanyl-preferring ribonucleases renews taxonomic status of two Bacillus strains

The potential of microbial ribonucleases as promising antitumor and antiviral agents, determines today's directions of their study. One direction is connected with biodiversity of RNases. We have analyzed completed and drafted Bacillus genomes deposited in GenBank for the presence of coding regions similar to the gene of an extracellular guanyl-preferring RNase of Bacillus amyloliquefaciens (barnase). Orthologues of the barnase gene were detected in 9 species out of 83. All of these belong to "B. subtilis" group within the genus. B. subtilis itself, as well as some other species within this group, lack such types of RNases. RNases similar to barnase were also found in species of "B. cereus" group as a part of plasmid-encoded S-layer toxins. It was also found that taxonomic states of culture collection strains, which were initially described based on a limited set of phenotypic characteristics, can be misleading and need to be confirmed. Using several approaches such as matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), sequencing of genes for 16S ribosomal RNA and RNA polymerase subunit beta followed by reconstruction of phylogenetic trees, we have re-identified two RNase-secreting Bacillus strains: B. thuringiensis B-388 which should be assigned as B. altitudinis B388 and B. intermedius 7P which should be renamed as B. pumilus 7P. Therefore, small secreted guanyl-preferring RNases are the feature of "B. subtilis" group only, which is characterized by distinctive lifestyle and adaptation strategies to environment.

Three-step procedure for preparation of pure Bacillus altitudinis ribonuclease

Ribonucleases are considered as promising tools for anticancer treatment due to their selective cytotoxicity against tumor cells. We investigated a new RNase from Bacillus altitudinis termed BALNASE (B. altitudinis RNase). Balnase is a close homolog of the well-known cytotoxic binase, differing by only one amino acid residue: nonpolar hydrophobic alanine at position 106 in the balnase molecule is replaced by a polar uncharged threonine in binase. The most exciting question is how the physico-chemical properties and biological effects of RNase might be changed by A106T substitution. Here, we have developed a chromatography-based rapid and modern technique for the purification of this new RNase which allowed us to get a protein sample of high quality with specific activity of 1.2 × 10(6) units in preparative amounts, suitable for further investigation of its biological properties.

Binase-like guanyl-preferring ribonucleases are new members of Bacillus PhoP regulon

Extracellular low-molecular weight guanyl-preferring ribonucleases (LMW RNases) of Bacillus sp. comprise a group of hydrolytic enzymes that share highly similar structural and catalytic characteristics with barnase, a ribonuclease from Bacillus amyloliquefaciens, and binase, a ribonuclease from Bacillus intermedius. Although the physical-chemical and catalytic properties of Bacillus guanyl-preferring ribonucleases are very similar, there is considerably more variation in the environmental conditions that lead to the induction of the genes encoding these RNases. Based on structural differences of their genes the guanyl-preferring ribonucleases have been sub-divided into binase-like and barnase-like groups. Here we show the ability of the key regulator of phosphate deficiency response, PhoP, to direct the transcription of the binase-like RNases but not barnase-like RNases. These results, together with our demonstration that binase-like RNases are induced in response to phosphate starvation, allow us to categorise this group of ribonucleases as new members of Bacillus PhoP regulon. In contrast, the barnase-like ribonucleases are relatively insensitive to the phosphate concentration and the environmental conditions that are responsible for their induction, and the regulatory elements involved, are currently unknown.