Environmental arsenic poisoning affects roughly 200 million people worldwide. The toxicity and mobility of arsenic in the environment is significantly influenced by microbial redox reactions, with arsenite (As ) being more toxic than arsenate (As ). Microbial oxidation of As to As is known to be regulated by the AioXSR signal transduction system and viewed to function for detoxification or energy generation. Here, we show that As oxidation is ultimately regulated by the phosphate starvation response (PSR), requiring the sensor kinase PhoR for expression of the As oxidase structural genes aioBA. The PhoRB and AioSR signal transduction systems are capable of transphosphorylation cross-talk, closely integrating As oxidation with the PSR. Further, under PSR conditions, As significantly extends bacterial growth and accumulates in the lipid fraction to the apparent exclusion of phosphorus. This could spare phosphorus for nucleic acid synthesis or triphosphate metabolism wherein unstable arsenic esters are not tolerated, thereby enhancing cell survival potential. We conclude that As oxidation is logically part of the bacterial PSR, enabling the synthesis of the phosphate analog As to replace phosphorus in specific biomolecules or to synthesize other molecules capable of a similar function, although not for total replacement of cellular phosphate.

Reports of biogenic methane (CH4) synthesis associated with a range of organisms have steadily accumulated in the literature. This has not happened without controversy and in most cases the process is poorly understood at the gene and enzyme levels. In marine and freshwater environments, CH4 supersaturation of oxic surface waters has been termed the “methane paradox” because biological CH4 synthesis is viewed to be a strictly anaerobic process carried out by O2-sensitive methanogens. Interest in this phenomenon has surged within the past decade because of the importance of understanding sources and sinks of this potent greenhouse gas. In our work on Yellowstone Lake in Yellowstone National Park, we demonstrate microbiological conversion of methylamine to CH4 and isolate and characterize an Acidovorax sp. capable of this activity. Furthermore, we identify and clone a gene critical to this process (encodes pyridoxylamine phosphate-dependent aspartate aminotransferase) and demonstrate that this property can be transferred to Escherichia coli with this gene and will occur as a purified enzyme. This previously unrecognized process sheds light on environmental cycling of CH4, suggesting that O2-insensitive, ecologically relevant aerobic CH4 synthesis is likely of widespread distribution in the environment and should be considered in CH4 modeling efforts.

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Pyrrolizidine alkaloids are natural secondary metabolites that are mainly produced in plants, bacteria, and fungi as a part of an organism’s defense machinery. These compounds constitute the largest class of alkaloids and are produced in nearly 3% of flowering plants, most of which belong to the Asteraceae and Boraginaceae families. Chemically, pyrrolizidine alkaloids are esters of the amino alcohol necine (which consists of two fused five-membered rings including a nitrogen atom) and one or more units of necic acids. Pyrrolizidine alkaloids are toxic to humans and mammals; thus, the ability to detect these alkaloids in food and nutrients is a matter of food security. The latest advances in the extraction and analysis of this class of alkaloids are summarized in this review, with special emphasis on chromatographic-based analysis and determinations in food.

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Halal status of ethanol resulting from natural fermentation in food is controversial. According to the GSO standard (2538:2017), the maximum residue level (MRL) of ethanol in fruit juices is 0.1% (v/v). This study examined the effect of storage duration on the formation of ethanol and sugar content in fruit juices. A total of 49 different fruit juice samples (orange, apple, berry, pineapple, and a mixture of grapes and berries) were purchased from local supermarkets and analyzed for ethanol by HS-GC-FID and sugar content (glucose, fructose, and sucrose) by HPLC-RID. The samples were stored in the refrigerator (2-5℃) throughout the experiment and analyzed every week for one month during validity period. Results showed that all juices' ethanol levels were below the MRL 0.1% (v/v) and ranged from ˂ (LOQ: 0.02%) (orange, apple, and berry juices) up to 0.076% (v/v) (in mixed grape and berry juice), while total sugar content ranged from 6.5% (v/v) in orange juice up to 12.6% (v/v) in grape and berry mix juice. Ethanol levels and sugar content in all juices remained constant throughout the experiment, indicating that the fermentation process is inactive during storage and that of ethanol MRL in GSO standard is appropriate.