2-phenylethanol (2-PE) is a rose-scented aromatic alcohol commonly used in the food, cosmetic, and pharmaceutical industries. The physical and chemical production methods of 2-PE are not suitable for industrial application due to the low yields. As a single-celled eukaryotic microorganism, yeast has the potential to efficiently synthesize natural 2-PE. Therefore, the strategy of using yeast as a chassis microorganism to synthesize 2-PE is favored by researchers. However, during the fermentation for 2-PE production, the yeast is inevitably affected by the toxic effects of 2-PE. Therefore, there is an urgent need to investigate the mechanisms of yeast tolerance to 2-PE, which will provide a theoretical basis for production practice and help to select yeast strains with high tolerance to 2-PE. In this paper, we review the research advances in 2-PE tolerance of yeast from the synthetic pathways of 2-PE and yeast tolerance mechanisms and introduce the methods for improving the 2-PE tolerance of yeast. Deciphering the mechanism of yeast tolerance to 2-PE for improving the yield and conversion efficiency of 2-PE in yeast is a top priority for the future research.

Pyrroloquinoline quinone (PQQ), the third oxidoreductase coenzyme discovered in the nature after nicotinamide and riboflavin, is ubiquitous in bacteria, fungi, plants, and animals. PQQ participates in a variety of life activities and has anti-inflammation, anti-oxidation, cell metabolism-enhancing, and cardioprotective activities, demonstrating broad application prospects in pharmaceuticals, agriculture, food and other fields. Therefore, the large-scale production of PQQ is the primary problem that needs to be solved at present. Microbial fermentation is a primary production method of PQQ. Deciphering the biosynthesis pathway and regulatory mechanism of PQQ is essential for the screening and breeding of strains with short production periods and high yields by metabolic engineering, which has been a hot topic in this field. This paper summarizes the synthesis pathways, strain screening and breeding, microbial production, and purification processes of PQQ, aiming to provide a reference for further research and application of PQQ.

People are exposed to environments containing various pathogens, which have multiple interactions with human cells or tissues. Pathogens can survive in the host environment by regulating pathogenic conditions such as virulence and invasiveness. At the same time, host cells resist the invasion of pathogens by mobilizing their own immune system. However, researchers mainly focus on the physiological functions of sRNAs in pathogens and have gained limited knowledge about the interactions between pathogens and hosts. How to use highly sensitive and high-resolution methods to study the interactions between pathogens and hosts have become a major challenge in the current research. By reviewing relevant studies, we summarize the commonly used techniques and experimental processes for studying the interactions between pathogens and hosts, aiming to improve the understanding about the mechanisms and principles of these experimental techniques and provide technical references for the research on interactions between pathogen sRNAs and host targets.

In bacterial cells, RNase HI usually degrades RNA in the RNA/DNA hybrids to prevent the accumulation of primers in replication and the formation of R-loops in transcription, thus maintaining genomic stability and normal life activities. The recognition of substrates by RNase HI mainly depends on DNA- and RNA-binding grooves, and the catalysis of substrates by RNase HI mainly depends on the DEDD motif and a histidine located in a flexible loop near the active site. Metal ions represented by Mg²⁺ play an important role in the catalytic process. The mode of action of RNase HI is determined by the type of ssDNA overhangs on RNA/DNA hybrids. In the presence of a 5' ssDNA overhang or in the absence of any overhang on RNA/DNA hybrids, RNase HI functions as a non-sequence-specific endonuclease to degrade RNA randomly. In the presence of a 3' ssDNA overhang on RNA/DNA hybrids, RNase HI relies on 5'-exonuclease activity for the successive degradation of RNA. RNase HI, Rep, DinG, and UvrD are recruited near the replication forks by interacting with the six residues of the C-terminal tail of single-stranded DNA-binding protein (SSB), and may resolve replication-transcription conflicts in a cooperative manner. The deletion of RNase HI or the decrease in RNase HI activity will cause a series of harmful events such as DNA structural instability, gene mutation, transcriptional machinery backtracking, and replication incoordination. RNase HI has shown great application prospects in antisense technology, R-loop detection, and targeted therapy combined with antibiotics. The cooperative mechanism of primer degradation by RNase HI and other enzymes is also worth studying in the future.