From natural to artificial cyanophages: Current progress and application prospects

Extra peptidase of a cyanophage confers its stronger lytic effect on bloom-forming Microcystis aeruginosa

Microcystis covers important cyanobacteria species that causes harmful algal blooms. Cyanophages are viruses that infect and lyse cyanobacteria and have been considered as potential cyanobacteria control strategy. Present study isolated two cyanophage strains, MaMV-CH01 (CH01) and MaMV-CH02 (CH02), infecting M. aeruginosa. Growth curves showed that CH01 has a stronger proliferation ability and host cell lysis capability than CH02. Combined with genomic, gene structure and function analysis, as well as biologic testing including infectivity, we confirmed that there is widespread horizontal gene transfer between the cyanophages and cyanobacteria, enabling the cyanophages to carry a series of auxiliary metabolic genes (AMG) related to host's metabolism. Moreover, compared with CH02, the cyanophage CH01 carrying extra AMG, a peptidase encoding gene (82R), exhibited stronger lytic activity against its host. Expression of CH01 82R in vitro showed strong bacteriostatic activity. Further, testing the cyanophage's ability to form plaques showed that the CH01(AMG+), which encodes the aforementioned peptidase, can form larger plaques, with an area of about threefold than that formed by CH02(AMG-). Above results indicated that the cyanophages with specific peptidase possessed stronger algicidal efficiency, which provided a direction for finding efficient cyanophages to regulate the population of bloom-forming cyanobacteria.

Expression and characterization of the complete cyanophage genome PP in the heterologous host Synechococcus elongatus PCC 7942

In this study, we successfully integrated the full-length genome of the cyanophage PP into the non-host cyanobacterium Synechococcus elongatus PCC 7942, facilitated by conjugation via Escherichia coli. To address the challenge posed by the toxic open reading frames (ORFs) of PP in E. coli, we first identified and characterized three toxic ORFs. The PP genome was subsequently rearranged, and the expression of these toxic ORFs was controlled using a tandem-induction switch system. The full-length PP genome was then successfully integrated into the genome of S. elongatus PCC 7942. Interestingly, the integration of the PP genome led to a reduction in photosynthesis and carbon fixation in S. elongatus PCC 7942, resembling the effects typically associated with cyanophage infection. Transcriptomic analysis showed that 32 of the 41 ORFs in the PP genome were actively transcribed in S. elongatus PCC 7942, significantly affecting energy metabolism and carbon fixation pathways. These effects were further confirmed by metabolomic analysis.

Cyanophage Engineering for Algal Blooms Control

Cyanobacteria represent a prevalent category of photosynthetic autotrophs capable of generating deleterious algal blooms, commonly known as cyanobacteria harmful algal blooms (cyanoHABs). These blooms often produce cyanotoxins, which pose risks to public health and ecosystems by contaminating surface waters and drinking water sources. Traditional treatment methods have limited effectiveness. Therefore, there is an urgent need for a new approach to effectively manage cyanoHABs. One promising approach is the use of cyanophages, which are viruses that specifically target cyanobacteria. Cyanophages serve as an effective biological control method for reducing cyanoHABs in aquatic systems. By engineering cyanophages, it is possible to develop a highly specific control strategy that minimally impacts non-target species and their propagation in the environment. This review explores the potential application of cyanophages as a strategy for controlling cyanoHABs. It includes the identification and isolation of broad-spectrum and novel cyanophages, with a specific focus on freshwater Microcystis cyanophages, highlighting their broad spectrum and high efficiency. Additionally, recent advancements in cyanophage engineering are discussed, including genome modification, functional gene identification, and the construction of artificial cyanophages. Furthermore, the current state of application is addressed. Cyanophage is a promising control strategy for effectively managing cyanoHABs in aquatic environments.

CRISPR/Cas12a-based genome editing for cyanophage of Anabeana sp

Efforts have been conducted on cyanobacterial genome editing, yet achieving genome editing in cyanophages remains challenging. Editing cyanophage genomes is crucial for understanding and manipulating their interactions with cyanobacterial hosts, offering potential solutions for controlling cyanobacterial blooms. In this study, we developed a streamlined CRISPR-Cas12a-based method for efficient cyanophage genome editing and then applied this method to the cyanophages A-1(L) and A-4(L) of Anabeana sp. PCC.7120. Multiple hypothetical genes were edited and knocked out from these two cyanophage genomes, generating viable mutants with varying capabilities to inhibit cyanobacterial growth. All these mutants displayed significant inhibitory effects on the host, indicating that these genes were non-essential for phage life cycle and the deletion led to little impairment of the cyanophages in infectious efficiency to their host. By iterative and simultaneous gene knockouts in cyanophage A-4(L), we achieved the minimal genome mutant with a 2400 bp reduction in genome size, representing a 5.75 % decrease compared to the wild type (WT). In conclusion, these cyanophage mutants can facilitate the identification of nonessential genes for cyanophages biology and the insertion of foreign genes for synthetic biology research. This advancement holds promise in addressing the widespread issue of water blooms and the associated environmental hazards.

Biotechnological approaches for suppressing Microcystis blooms: insights and challenges

Cyanobacterial harmful algal blooms, particularly those dominated by Microcystis, pose significant ecological and health risks worldwide. This review provides an overview of the latest advances in biotechnological approaches for mitigating Microcystis blooms, focusing on cyanobactericidal bacteria, fungi, eukaryotic microalgae, zooplankton, aquatic plants, and cyanophages. Recently, promising results have been obtained using cyanobactericidal bacteria: not through the inoculation of cultured bacteria, but rather by nurturing those already present in the periphyton or biofilms of aquatic plants. Fungi and eukaryotic microalgae also exhibit algicidal properties; however, their practical applications still face challenges. Zooplankton grazing on Microcystis can improve water quality, but hurdles exist because of the colonial form and toxin production of Microcystis. Aquatic plants control blooms through allelopathy and nutrient absorption. Although cyanophages hold promise for Microcystis control, their strain-specificity hinders widespread use. Despite successful laboratory validation, field applications of biological methods are limited. Future research should leverage advanced molecular and bioinformatic techniques to understand microbial interactions during blooms and offer insights into innovative control strategies. Despite progress, the efficacy of biological methods under field conditions requires further verification, emphasizing the importance of integrating advanced multi-meta-omics techniques with practical applications to address the challenges posed by Microcystis blooms. KEY POINTS: • A diverse range of biotechnological methods is presented for suppressing Microcystis blooms. • Efficacy in laboratory experiments needs to be proved further in field applications. • Multi-meta-omics techniques offer novel insights into Microcystis dynamics and interactions.

Efficient Broad-Spectrum Cyanophage Function Module Mining

Cyanobacterial harmful algal blooms (CyanoHABs) cause health and environmental effects worldwide. Cyanophage is a virus that exclusively infects cyanobacteria. Using cyanophages to control blooms is the latest biological control method. However, little research on the genomics of cyanophages and the presence of numerous proteins with unidentified functions in cyanophage genomes pose challenges for their practical application and comprehensive investigation. We selected the broad-spectrum and efficient cyanophage YongM for our study. On the one hand, through rational analysis, we analyze essential genes, establish the minimal cyanophage genome and single essential gene modules, and examine the impact of essential modules on growth. Additionally, we conducted ultraviolet mutagenesis on YongM to generate more efficient cyanophages' critical modules through random mutagenesis. Then, we sequenced and analyzed the functionality of the mutational gene modules. These findings highlight several gene modules that contribute to a deeper understanding of the functional components within cyanophage genomes.

Advanced protein nanobiosensors to in-situ detect hazardous material in the environment

Determining hazardous substances in the environment is vital to maintaining the safety and health of all components of society, including the ecosystem and humans. Recently, protein-based nanobiosensors have emerged as effective tools for monitoring potentially hazardous substances in situ. Nanobiosensor detection mode is a combination of particular plasmonic nanomaterials (e.g., nanoparticles, nanotubes, quantum dots, etc.), and specific bioreceptors (e.g., aptamers, antibodies, DNA, etc.), which has the benefits of high selectivity, sensitivity, and compatibility with biological systems. The role of these nanobiosensors in identifying dangerous substances (e.g., heavy metals, organic pollutants, pathogens, toxins, etc.) is discussed along with different detection mechanisms and various transduction methods (e.g., electrical, optical, mechanical, electrochemical, etc.). In addition, topics discussed include the design and construction of these sensors, the selection of proteins, the integration of nanoparticles, and their development processes. A discussion of the challenges and prospects of this technology is also included. As a result, protein nanobiosensors are introduced as a powerful tool for monitoring and improving environmental quality and community safety.