An Acrylamide-degrading Bacterial Consortium Isolated from Volcanic Soi

In soil, polyacrylamide is a key source of acrylamide because it slowly decomposes into acrylamide. There has been a modest but steady rise in worldwide interest in microbe-mediated acrylamide decomposition as a bioremediation method. A bacterial consortium isolated from the volcanic soil of Mount Marapi, West Sumatra, Indonesia, was able to thrive on acrylamide in this study. Acrylamide-degrading bacteria grew best in the presence of 1 %(w/v) glucose with acrylamide as the sole nitrogen source. Optimum growth occurs in between 300 and 500 mg/L of acrylamide, pH between 6.5 and 8.0, and temperatures between 30 and 35 °C. The consortium can also grow on acetamide as the sole nitrogen source. Toxic heavy metals, such as mercury, silver and copper slowed down the growth of this consortium on acrylamide. This is the first report of an acrylamide-degrading consortium isolated from volcanic soils.

Alternative Pathway for 3-Cyanoalanine Assimilation in Pseudomonas pseudoalcaligenes CECT5344 under Noncyanotrophic Conditions

Nitriles are organic cyanides with important industrial applications, but they are also found in nature. 3-Cyanoalanine is synthesized by plants and some bacteria to detoxify cyanide from endogenous or exogenous sources, but this nitrile may be also involved in other processes such as stress tolerance, nitrogen and sulfur metabolism, and signaling. The cyanide-degrading bacterium Pseudomonas pseudoalcaligenes CECT5344 grows with 3-cyanoalanine as the sole nitrogen source, but it does not use this nitrile as an intermediate in the cyanide assimilation pathway.

Filling in the Gaps in Metformin Biodegradation: A New Enzyme and a Metabolic Pathway for Guanylurea

The widely prescribed pharmaceutical metformin and its main metabolite guanylurea are currently two of the most common contaminants in surface and wastewater. Guanylurea often accumulates and is poorly, if at all, biodegraded in wastewater treatment plants. This study describes Pseudomonas mendocina strain GU isolated from a municipal wastewater treatment plant using guanylurea as its sole nitrogen source. The genome was sequenced with 36-fold coverage and mined to identify guanylurea degradation genes. The gene encoding the enzyme initiating guanylurea metabolism was expressed, the enzyme purified and characterized. Guanylurea hydrolase, a newly described enzyme, was shown to transform guanylurea to one equivalent of ammonia and guanidine. Guanidine also supports growth as a sole nitrogen source. Cell yields from growth on limiting concentrations of guanylurea revealed that metabolism releases all four nitrogen atoms. Genes encoding complete metabolic transformation were identified bioinformatically, defining the pathway as follows: guanylurea to guanidine to carboxyguanidine to allophanate to ammonia and carbon dioxide. The first enzyme, guanylurea hydrolase, is a member of the isochorismatase-like hydrolase protein family that includes biuret hydrolase and triuret hydrolase. Although homologs, the three enzymes show distinct substrate specificities. Pairwise sequence comparisons and the use of sequence similarity networks allowed fine structure discrimination between the three homologous enzymes and provided insights into the evolutionary origins of guanylurea hydrolase. IMPORTANCE Metformin is a pharmaceutical most prescribed for type 2 diabetes and is now being examined for potential benefits to COVID-19 patients. People taking the drug pass it largely unchanged and it subsequently enters wastewater treatment plants. Metformin has been known to be metabolized to guanylurea. The levels of guanylurea often exceed that of metformin, leading to the former being considered a “dead end” metabolite. Metformin and guanylurea are water pollutants of emerging concern as they persist to reach non-target aquatic life and humans, the latter if it remains in treated water. The present study has identified a Pseudomonas mendocina strain that completely degrades guanylurea. The genome was sequenced and the genes involved in guanylurea metabolism were identified in three widely separated genomic regions. This knowledge advances the idea that guanylurea is not a dead end product and will allow for bioinformatic identification of the relevant genes in wastewater treatment plant microbiomes and other environments subjected to metagenomic sequencing.

Solvent-assisted strategy induced surface N-modification of PtCu aerogel for enhanced electrocatalytic property

A facile method of surface nitrogen modification of PtCu aerogels with N-Methyl pyrrolidone as the sole nitrogen source is reported. The E1/2 of PtCu aerogels is 0.932 V and the...

An opaque cell-specific expression program of secreted proteases and transporters allows cell-type cooperation in Candida albicans

An unusual feature of the opportunistic pathogen C. albicans is its ability to stochastically switch between two distinct, heritable cell types called white and opaque. Here, we show that only opaque cells, in response to environmental signals, massively up-regulate a specific group of secreted proteases and peptide transporters, allowing exceptionally efficient use of proteins as sources of nitrogen. We identify the specific proteases (members of the secreted aspartyl protease (SAP) family) needed for opaque cells to proliferate under these conditions, and we identify four transcriptional regulators of this specialized proteolysis and uptake program. We also show that, in mixed cultures, opaque cells enable white cells to also proliferate efficiently when proteins are the sole nitrogen source. Based on these observations, we suggest that one role of white-opaque switching is to create mixed populations where the different phenotypes derived from a single genome are shared between two distinct cell types.SummaryThe opportunistic human fungal pathogen Candida albicans switches between two distinct, heritable cell types, named “white” and “opaque.” We show that opaque cells, in response to proteins as the sole nitrogen source, up-regulate a specialized program, including specific secreted aspartyl proteases and peptide transporters. We demonstrate that, in mixed cultures, opaque cells enable white cells to respond and proliferate more efficiently under these conditions. These observations suggest that white-opaque switching creates mixtures of cells where the population characteristics - which derive from a single genome - reflect the contributions of two distinct cell types.Dataset Reference NumbersThe .RAW files for both sets of Mass Spectrometry experiments have been deposited at the ProteoSAFe resource (https://proteomics.ucsd.edu/ProteoSAFe/).MSP-MS experiment reference number: MSV000085279. For reviewer access use login “MSV000085279_reviewer” and password “candidamspms”.Proteomics experiment reference number: MSV000085283. For reviewer access use login “MSV000085283_reviewer” and password “candidaprot”.

Multidimensional Reveal of Nitrogen Regulation on Comammox

Background The discovery of complete ammonia oxidizer (comammox) was groundbreaking. Comammox can use ammonia as the sole nitrogen source and turn it to nitrate. Moreover, genomic data indicated that comammox contained genes which can metabolize urea and nitrite. However, the feasibility of enriching comammox with urea and nitrite in long term has not been proved. This study enriched comammox’s culture by using nitrite in reactor SA and urea in reactor SB. Results The nitrification rate of reactor SB (1.29 mg N·g -1 biofilm · d -1 ) was higher than that in reactor SA (0.6 mg N · g -1 biofilm · d -1 ) at the 390 th day. Comammox outnumbered ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in both reactor SA (9.04 × 10 9 copies / g biofilm) and reactor SB (5.34×10 10 copies/ g biofilm). In reactor SA, comammox’s amoA accounted for 92% of the total amoA, which was higher than that in reactor SB (85%). However, the percentage of comammox (4%) in total bacteria was much lower than reactor SB (14%). The results of metagenomic sequencing showed that all the pathways of nitrogen cycle including nitrification, nitrogen fixation, denitrification, assimilation nitrate reduction, and dissimilation nitrate reduction can be detected in both reactor SA and reactor SB except the anammox pathway. The genes related to nitrite oxidation and nitrate reduction in reactor SA (TPM = 5099; TPM = 3329) was higher than that of in reactor SB (TPM = 4071; TPM = 2984), presumably due to the demand of turning nitrite to nitrate and turning nitrate to ammonia. While genes related to ammonia oxidation and urea metabolism in reactor SB (TPM = 3915; TPM = 3638) was higher than that in reactor SA (TPM = 2708; TPM = 3002). Conclusion Nitrite and urea can regulate the enrichment culture of comammox by converting its metabolic pathway. Using nitrite as sole nitrogen source can improve the proportion comammox’s amoA in total amoA while using urea as the sole nitrogen source may increase comammox’s proportion in total bacteria. These results can accelerate the enrichment of comammox and facilitate the promotion of comammox’s engineering operation.