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The gas vesicle (GV) is like a hollow nanoparticle consisting of an internal gas and a protein shell, which mainly consists of hydrophobic gas vesicle protein A (GvpA) and GvpC attached to the surface. GVs, first discovered in cyanobacteria, are mainly produced by photosynthetic bacteria (PSB) and halophilic archaea. After being modified and engineered, GVs can be utilized as contrast agents, delivery carriers, and immunological boosters for disease prevention, diagnosis, and treatment with good results due to their tiny size, strong stability and non-toxicity advantages. Many diagnostic and therapeutic approaches based on GV are currently under development. In this review, we discuss the source, function, physical and chemical properties of GV, focus on the current application progress of GV, and put forward the possible application prospect and development direction of GV in the future. [ABSTRACT FROM AUTHOR]

Abstract The gas vesicle (GV) is like a hollow nanoparticle consisting of an internal gas and a protein shell, which mainly consists of hydrophobic gas vesicle protein A (GvpA) and GvpC attached to the surface. GVs, first discovered in cyanobacteria, are mainly produced by photosynthetic bacteria (PSB) and halophilic archaea. After being modified and engineered, GVs can be utilized as contrast agents, delivery carriers, and immunological boosters for disease prevention, diagnosis, and treatment with good results due to their tiny size, strong stability and non-toxicity advantages. Many diagnostic and therapeutic approaches based on GV are currently under development. In this review, we discuss the source, function, physical and chemical properties of GV, focus on the current application progress of GV, and put forward the possible application prospect and development direction of GV in the future.

Nanoscale ultrasound contrast agents have attracted considerable interest in the medical imaging field for their ability to penetrate tumor vasculature and enable targeted imaging of cancer cells by attaching to tumor-specific ligands. Despite their potential, traditional chemically synthesized contrast agents face challenges related to complex synthesis, poor biocompatibility, and inconsistent imaging due to non-uniform particle sizes. To address these limitations, bio-synthesized nanoscale ultrasound contrast agents have been proposed as a viable alternative, offering advantages such as enhanced biocompatibility, consistent particle size for reliable imaging, and the potential for precise functionalization to improve tumor targeting. In this study, we successfully isolated cylindrical gas vesicles (GVs) from Serratia. 39006 and subsequently introduced the GVs-encoding gene cluster into Escherichia coli using genetic engineering techniques. We then characterized the contrast imaging properties of two kinds of purified GVs, using in vitro and in vivo methods. Our results demonstrated that naturally isolated GVs could produce stable ultrasound contrast signals in murine livers and tumors using clinical diagnostic ultrasound equipment. Additionally, heterologously expressed GVs from gene-engineered bacteria also exhibited good ultrasound contrast performance. Thus, our study presents favorable support for the application of genetic engineering techniques in the modification of gas vesicles for future biomedical practice. [ABSTRACT FROM AUTHOR]

Yanan Feng,1,2,* Yongsheng Hao,3,* Yuanyuan Wang,3 Weijian Song,1,4 Shanxin Zhang,1 Dong Ni,5 Fei Yan,3 Litao Sun1 1Cancer Center, Department of Ultrasound Medicine, Zhejiang Provincial People’s Hospital (Affiliated People’s Hospital), Hangzhou Medical College, Hangzhou, Zhejiang, 310014, People’s Republic of China; 2Department of Abdominal Ultrasound, The Affiliated Hospital of Qingdao University, Qingdao, Shandong, 266000, People’s Republic of China; 3Center for Cell and Gene Circuit Design, CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, People’s Republic of China; 4Bengbu Medical College, Bengbu, 233030, People’s Republic of China; 5Medical Ultrasound Image Computing (MUSIC) Laboratory, Shenzhen University, Shenzhen, 518055, People’s Republic of China*These authors contributed equally to this workCorrespondence: Litao Sun; Fei Yan, Tel +86 13946037056, Email litaosun1971@sina.com; fei.yan@siat.ac.cnPurpose: Ultrasound molecular imaging (UMI) has proven promising to diagnose the onset and progression of diseases such as angiogenesis, inflammation, and thrombosis. However, microbubble-based acoustic probes are confined to intravascular targets due to their relatively large particle size, greatly reducing the application value of UMI, especially for extravascular targets. Extradomain B fibronectin (ED-B FN) is an important glycoprotein associated with tumor genesis and development and highly expressed in many types of tumors. Here, we developed a gas vesicles (GVs)-based nanoscale acoustic probe (ZD2-GVs) through conjugating ZD2 peptides which can specially target to ED-B FN to the biosynthetic GVs.Materials and Methods: ED-B FN expression was evaluated in normal liver and tumor tissues with immunofluorescence and Western blot. ZD2-GVs were prepared by conjugating ZD2 to the surface of GVs by amide reaction. The inverted microscope was used to analyze the targeted binding capacity of ZD2-GVs to MB49 cells (bladder cancer cell line). The contrast-enhanced imaging features of GVs, non-targeted control GVs (CTR-GVs), and targeted GVs (ZD2-GVs) were compared in three MB49 tumor mice. The penetration ability of ZD2-GVs in tumor tissues was assessed by fluorescence immunohistochemistry. The biosafety of GVs was evaluated by CCK8, blood biochemistry, and HE staining.Results: Strong ED-B FN expression was observed in tumor tissues while little expression in normal liver tissues. The resulting ZD2-GVs had only 267.73 ± 2.86 nm particle size and exhibited excellent binding capability to the MB49 tumor cells. The in vivo UMI experiments showed that ZD2-GVs produced stronger and longer retention in the BC tumors than that of the non-targeted CTR-GVs and GVs. Fluorescence immunohistochemistry confirmed that ZD2-GVs could penetrate the tumor vascular into the interstitial space of the tumors. Biosafety analysis revealed there was no significant cytotoxicity to these tested mice.Conclusion: Thus, ZD2-GVs can function as a potential UMI probe for the early diagnosis of bladder cancer.Graphical Abstract: Keywords: ultrasound contrast agents, gas vesicles, ultrasound molecular imaging, tumor diagnosis

Nanoscale ultrasound contrast agents have attracted considerable interest in the medical imaging field for their ability to penetrate tumor vasculature and enable targeted imaging of cancer cells by attaching to tumor-specific ligands. Despite their potential, traditional chemically synthesized contrast agents face challenges related to complex synthesis, poor biocompatibility, and inconsistent imaging due to non-uniform particle sizes. To address these limitations, bio-synthesized nanoscale ultrasound contrast agents have been proposed as a viable alternative, offering advantages such as enhanced biocompatibility, consistent particle size for reliable imaging, and the potential for precise functionalization to improve tumor targeting. In this study, we successfully isolated cylindrical gas vesicles (GVs) from Serratia. 39006 and subsequently introduced the GVs-encoding gene cluster into Escherichia coli using genetic engineering techniques. We then characterized the contrast imaging properties of two kinds of purified GVs, using in vitro and in vivo methods. Our results demonstrated that naturally isolated GVs could produce stable ultrasound contrast signals in murine livers and tumors using clinical diagnostic ultrasound equipment. Additionally, heterologously expressed GVs from gene-engineered bacteria also exhibited good ultrasound contrast performance. Thus, our study presents favorable support for the application of genetic engineering techniques in the modification of gas vesicles for future biomedical practice.

Sonogenetics is an emerging approach that harnesses ultrasound for the manipulation of genetically modified cells. The great penetrability of ultrasound waves enables the non-invasive application of external stimuli to deep tissues, particularly advantageous for brain stimulation. Genetically encoded ultrasound mediators, a set of proteins that respond to ultrasound-induced bio-effects, play a critical role in determining the effectiveness and applications of sonogenetics. In this context, we will provide an overview of these ultrasound-responsive mediators, delve into the molecular mechanisms governing their response to ultrasound stimulation, and summarize their applications in neuromodulation.

Many aquatic ecosystems are seriously threatened by cyanobacteria blooms; gas vesicles enable cyanobacteria to form harmful cyanobacterial blooms rapidly. Many lake managers try to control cyanobacterial blooms by collapsing gas vesicle, but it is still unclear whether gas vesicle recovery will cause this method to fail. Through the culture experiments of three cyanobacteria, it was found that all cyanobacteria with collapsed gas vesicles can rapidly regain buoyancy in a few days under nutrient-sufficient environments, and average gas vesicle content was even 9% higher than initially. In contrast, buoyancy recovery of all cyanobacteria under nutrient-limited environments was significantly worse. After culture experiments, the average gas vesicle content of all cyanobacteria in phosphorus-limited environments only reach 49% of the initial value. The gas vesicle content of two non-nitrogen-fixing cyanobacteria in nitrogen-limited environments only reached 38% of initial value. The buoyancy of cyanobacteria in different tropic levels was similar to the gas vesicle content. These results indicate that collapsing gas vesicles can only control cyanobacterial blooms in the short-term. To control cyanobacterial blooms in the long-term, in deep lakes, lake managers should discharge gas vesicles' collapsed cyanobacteria into deep water. In shallow lakes, the disruption of gas vesicles must be combined with nutrient control measures to effectively control cyanobacteria blooms. [ABSTRACT FROM AUTHOR]

Jinghan Zhang,1 Fei Yan,2 Wei Zhang,1 Lei He,1 Yi Li,3 Shuai Zheng,1 Yuanyuan Wang,4 Tengfei Yu,1 Lijuan Du,1 Yuanyuan Shen,5 Wen He1 1Department of Ultrasound, Beijing Tiantan Hospital, Capital Medical University, Beijing, People’s Republic of China; 2Center for Cell and Gene Circuit Design, CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, People’s Republic of China; 3Department of Radiology, Peking Union Medical College Hospital, Beijing, People’s Republic of China; 4Department of Ultrasound, The Second Hospital of Hebei Medical University, Shijiazhuang, People’s Republic of China; 5National-Regional Key Technology Engineering Laboratory for Medical Ultrasound, School of Bio Medical Engineering, Health Science Center, Shenzhen University, Shenzhen, People’s Republic of ChinaCorrespondence: Yuanyuan Shen; Wen He, Email shenyy@szu.edu.cn; hewen@bjtth.orgBackground: Focused ultrasound (FUS) combined with microbubbles (MBs) has emerged as a potential approach for opening the blood–brain barrier (BBB) for delivering drugs into the brain. However, MBs range in size of microns and thus can hardly extravasate into the brain parenchyma. Recently, growing attention has been paid to gas vesicles (GVs), which are genetically encoded gas-filled nanostructures with protein shells, due to their potential for extravascular targeting in ultrasound imaging and therapy. However, the use of GVs as agents for BBB opening has not yet been investigated.Methods: In this study, GVs were extracted and purified from Halobacterium NRC-1. Ultrasound imaging performance of GVs was assessed in vitro and in vivo. Then, FUS/GVs-mediated BBB opening for small molecular Evans blue or large molecular liposome delivery across the BBB was examined.Results: The results showed a good contrast performance of GVs for brain perfusion ultrasound imaging in vivo. At the acoustic negative pressure of 1.5 MPa, FUS/GVs opened the BBB safely, and effectively enhanced Evans blue and 200-nm liposome delivery into the brain parenchyma.Conclusion: Our study suggests that biosynthetic GVs hold great potential to serve as local BBB-opening agents in the development of new targeted drug delivery strategies for central nervous system disorders.Keywords: gas vesicles, blood–brain barrier, focused ultrasound, drug delivery, nanoparticles

The present study aimed to use comparative genomics to explore the relationships between Frankia and actinorhizal plants using a data set made of 33 Frankia genomes. The determinants of host specificity were first explored for "Alnus-infective strains" (i.e., Frankia strains belonging to Cluster Ia). Several genes were specifically found in these strains, including an agmatine deiminase which could possibly be involved in various functions as access to nitrogen sources, nodule organogenesis or plant defense. Within "Alnus-infective strains", Sp+ Frankia genomes were compared to Sp− genomes in order to elucidate the narrower host specificity of Sp+ strains (i.e., Sp+ strains being capable of in planta sporulation, unlike Sp− strains). A total of 88 protein families were lost in the Sp+ genomes. The lost genes were related to saprophytic life (transcriptional factors, transmembrane and secreted proteins), reinforcing the proposed status of Sp+ as obligatory symbiont. The Sp+ genomes were also characterized by a loss of genetic and functional paralogs, highlighting a reduction in functional redundancy (e.g., hup genes) or a possible loss of function related to a saprophytic lifestyle (e.g., genes involved in gas vesicle formation or recycling of nutrients). [ABSTRACT FROM AUTHOR]

ABSTRACT The scale of post-transcriptional regulation and the implications of its interplay with other forms of regulation in environmental acclimation are underexplored for organisms of the domain Archaea. Here, we have investigated the scale of post-transcriptional regulation in the extremely halophilic archaeon Halobacterium salinarum NRC-1 by integrating the transcriptome-wide locations of transcript processing sites (TPSs) and SmAP1 binding, the genome-wide locations of antisense RNAs (asRNAs), and the consequences of RNase_2099C knockout on the differential expression of all genes. This integrated analysis has discovered that 54% of all protein-coding genes in the genome of this haloarchaeon are likely targeted by multiple mechanisms for putative post-transcriptional processing and regulation, with about 20% of genes likely being regulated by combinatorial schemes involving SmAP1, asRNAs, and RNase_2099C. Comparative analysis of mRNA levels (transcriptome sequencing [RNA-Seq]) and protein levels (sequential window acquisition of all theoretical fragment ion spectra mass spectrometry [SWATH-MS]) for 2,579 genes over four phases of batch culture growth in complex medium generated additional evidence for the conditional post-transcriptional regulation of 7% of all protein-coding genes. We demonstrate that post-transcriptional regulation may act to fine-tune specialized and rapid acclimation to stressful environments, e.g., as a switch to turn on gas vesicle biogenesis to promote vertical relocation under anoxic conditions and modulate the frequency of transposition by insertion sequence (IS) elements of the IS200/IS605, IS4, and ISH3 families. Findings from this study are provided as an atlas in a public Web resource (https://halodata.systemsbiology.net). IMPORTANCE While the transcriptional regulation landscape of archaea has been extensively investigated, we currently have limited knowledge about post-transcriptional regulation and its driving mechanisms in this domain of life. In this study, we collected and integrated omics data from multiple sources and technologies to infer post-transcriptionally regulated genes and the putative mechanisms modulating their expression at the protein level in Halobacterium salinarum NRC-1. The results suggest that post-transcriptional regulation may drive environmental acclimation by regulating hallmark biological processes. To foster discoveries by other research groups interested in the topic, we extended our integrated data to the public in the form of an interactive atlas (https://halodata.systemsbiology.net).

Nanobubbles have received great attention in ultrasound molecular imaging due to their capability to pass through the vasculature and reach extravascular tissues. Recently, gas vesicles (GVs) from archaea have been reported as acoustic contrast agents, showing great potential for ultrasound molecular imaging. However, the immunogenicity and biosafety of GVs has not yet been investigated. In this study, we examined the immune responses and biosafety of biosynthetic GVs and polyethylene glycol (PEG)-modified GVs (PEG-GVs) in vivo and in vitro. Our findings suggest that the plain GVs showed significantly stronger immunogenic response than PEG-GVs. Less macrophage clearance rate of the RES and longer circulation time were also found for PEG-GVs, thereby producing the better contrast imaging effect in vivo. Thus, our study demonstrated the PEG modification of biosynthetic GVs from Halobacterium NRC-1 is helpful for the future application of GVs in molecular imaging and treatment.

Huan Long,1,2,* Xiaojuan Qin,3,* Rui Xu,1,2 Chunlei Mei,4 Zhiyong Xiong,5 Xuan Deng,1 Kaiyao Huang,1,2 Huageng Liang5 1Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei Province, 430072, People’s Republic of China; 2University of Chinese Academy of Sciences, Beijing, 100049, People’s Republic of China; 3Department of Ultrasound, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, People’s Republic of China; 4Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, People’s Republic of China; 5Department of Urology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, People’s Republic of China*These authors contributed equally to this workCorrespondence: Kaiyao Huang; Huageng Liang Email leonard19800318@hust.edu.cn; huangky@ihb.ac.cnIntroduction: Ultrasonic molecular imaging (UMI) technology has attracted increasing interest because of its low cost and capability to evaluate changes rapidly and noninvasively at the cellular and molecular levels. The key material of this technology is ultrasound-responsive gas vesicles (GVs). GVs synthesized by conventional chemical methods have several limitations, such as high costs, low yields, and complex production processes. In comparison, biosynthesized GVs have the advantages of high stability, a low risk of toxicity, genetic engineering characterization, easy post modification and drug loading potential. However, translational studies of their biosynthesis are still in their infancy; in particular, the duration of GVs in the circulatory system is essential for the usage of UMI in biomedicine and the clinic.Results: Here, we report novel GVs biosynthesized by the cyanobacterium Microcystis, which have a moderate size, a negative zeta potential, a rod-like morphology, and a protein-shelled gas-contained structure. These GVs without any chemical modifications could be detected in the mice circulatory system for more than 10 hours by clinically used ultrasound scanners. In particular, GVs can accumulate in tumors via the enhanced permeation and retention (EPR) effect 11 hours post-injection, and lasting at least 2 hours, which might be a potential aid for tumor diagnosis. Furthermore, pathological and hematological study suggested that GVs are safe for the host.Conclusion: We concluded that the GVs synthesized by Microcystis without any modifications have UMI potential for systemic evaluation as well as tumoral diagnosis after intravenous injection.Keywords: ultrasonic molecular imaging, gas vesicles, biosynthesis

The formation of gas vesicles has been investigated in bacteria and haloarchaea for more than 50 years. These air-filled nanostructures allow cells to stay at a certain height optimal for growth in their watery environment. Several gvp genes are involved and have been studied in Halobacterium salinarum, cyanobacteria, Bacillus megaterium, and Serratia sp. ATCC39006 in more detail. GvpA and GvpC form the gas vesicle shell, and additional Gvp are required as minor structural proteins, chaperones, an ATP-hydrolyzing enzyme, or as gene regulators. We analyzed the Gvp proteins of Hbt. salinarum with respect to their protein–protein interactions, and developed a model for the formation of these nanostructures. Gas vesicles are also used in biomedical research. Since they scatter waves and produce ultrasound contrast, they could serve as novel contrast agent for ultrasound or magnetic resonance imaging. Additionally, gas vesicles were engineered as acoustic biosensors to determine enzyme activities in cells. These applications are based on modifications of the surface protein GvpC that alter the mechanical properties of the gas vesicles. In addition, gas vesicles have been decorated with GvpC proteins fused to peptides of bacterial or viral pathogens and are used as tools for vaccine development. [ABSTRACT FROM AUTHOR]

Gas vesicles (GVs) from microorganisms are genetically air-filled protein nanostructures, and serve as a new class of nanoscale contrast agents for ultrasound imaging. Recently, the genetically encoded GV gene clusters have been heterologously expressed in Escherichia coli, allowing these genetically engineered bacteria to be visualized in vivo in a real-time manner by ultrasound. However, most of the GV genes remained functionally uncharacterized, which makes it difficult to regulate and modify GVs for broad medical applications. Here, the impact of GV proteins on GV formation is systematically investigated. The results first uncovered that the deletions of GvpR or GvpU resulted in the formation of a larger proportion of small, biconical GVs compared to the full-length construct, and the deletion of GvpT resulted in a larger portion of large GVs. Meanwhile, the combination of gene deletions has resulted in several genotypes of ultrasmall GVs that span from 50 to 20 nm. Furthermore, the results showed that E. coli carrying the ΔGvpCRTU mutant can produce strong ultrasound contrast signals in mouse liver. In conclusion, the study provides new insights into the roles of GV proteins in GV formation and produce ultrasmall GVs with a wide range of in vivo research., (© 2024 Wiley‐VCH GmbH.)

A major challenge in the fields of biological imaging and synthetic biology is noninvasively visualizing the functions of natural and engineered cells inside opaque samples such as living animals. One promising technology that addresses this limitation is ultrasound (US), with its penetration depth of several cm and spatial resolution on the order of 100 μm. Within the past decade, reporter genes for US have been introduced and engineered to link cellular functions to US signals via heterologous expression in commensal bacteria and mammalian cells. These acoustic reporter genes (ARGs) represent a novel class of genetically encoded US contrast agent, and are based on air-filled protein nanostructures called gas vesicles (GVs). Just as the discovery of fluorescent proteins was followed by the improvement and diversification of their optical properties through directed evolution, here we describe the evolution of GVs as acoustic reporters. To accomplish this task, we establish high-throughput, semiautomated acoustic screening of ARGs in bacterial cultures and use it to screen mutant libraries for variants with increased nonlinear US scattering. Starting with scanning site saturation libraries for two homologues of the primary GV structural protein, GvpA/B, two rounds of evolution resulted in GV variants with 5- and 14-fold stronger acoustic signals than the parent proteins. We anticipate that this and similar approaches will help high-throughput protein engineering play as large a role in the development of acoustic biomolecules as it has for their fluorescent counterparts.

Ultrasound imaging and ultrasound-mediated gene and drug delivery are rapidly advancing diagnostic and therapeutic methods; however, their use is often limited by the need for microbubbles, which cannot transverse many biological barriers due to their large size. Here, the authors introduce 50-nm gas-filled protein nanostructures derived from genetically engineered gas vesicles(GVs) that are referred to as 50 nm GVs. These diamond-shaped nanostructures have hydrodynamic diameters smaller than commercially available 50-nm gold nanoparticles and are, to the authors' knowledge, the smallest stable, free-floating bubbles made to date. 50 nm GVs can be produced in bacteria, purified through centrifugation, and remain stable for months. Interstitially injected 50 nm GVs can extravasate into lymphatic tissues and gain access to critical immune cell populations, and electron microscopy images of lymph node tissues reveal their subcellular location in antigen-presenting cells adjacent to lymphocytes. The authors anticipate that 50 nm GVs can substantially broaden the range of cells accessible to current ultrasound technologies and may generate applications beyond biomedicine as ultrasmall stable gas-filled nanomaterials., (© 2024 Wiley‐VCH GmbH.)

Nanotechnology offers significant advantages for medical imaging and therapy, including enhanced contrast and precision targeting. However, integrating these benefits into ultrasonography is challenging due to the size and stability constraints of conventional bubble-based agents. Here bicones, truly tiny acoustic contrast agents based on gas vesicles (GVs), a unique class of air-filled protein nanostructures naturally produced in buoyant microbes, are described. It is shown that these sub-80 nm particles can be effectively detected both in vitro and in vivo, infiltrate tumors via leaky vasculature, deliver potent mechanical effects through ultrasound-induced inertial cavitation, and are easily engineered for molecular targeting, prolonged circulation time, and payload conjugation., (© 2024 The Authors. Advanced Materials published by Wiley‐VCH GmbH.)

Many aquatic ecosystems are seriously threatened by cyanobacteria blooms; gas vesicles enable cyanobacteria to form harmful cyanobacterial blooms rapidly. Many lake managers try to control cyanobacterial blooms by collapsing gas vesicle, but it is still unclear whether gas vesicle recovery will cause this method to fail. Through the culture experiments of three cyanobacteria, it was found that all cyanobacteria with collapsed gas vesicles can rapidly regain buoyancy in a few days under nutrient-sufficient environments, and average gas vesicle content was even 9% higher than initially. In contrast, buoyancy recovery of all cyanobacteria under nutrient-limited environments was significantly worse. After culture experiments, the average gas vesicle content of all cyanobacteria in phosphorus-limited environments only reach 49% of the initial value. The gas vesicle content of two non-nitrogen-fixing cyanobacteria in nitrogen-limited environments only reached 38% of initial value. The buoyancy of cyanobacteria in different tropic levels was similar to the gas vesicle content. These results indicate that collapsing gas vesicles can only control cyanobacterial blooms in the short-term. To control cyanobacterial blooms in the long-term, in deep lakes, lake managers should discharge gas vesicles’ collapsed cyanobacteria into deep water. In shallow lakes, the disruption of gas vesicles must be combined with nutrient control measures to effectively control cyanobacteria blooms.

Ultrasound contrast agents are valuable for diagnostic imaging and drug delivery. Generally, chemically synthesized microbubbles (MBs) are micro-sized particles. Particle size is a limiting factor for the diagnosis and treatment of many extravascular diseases. Recently, gas vesicles (GVs) from some marine bacteria and archaea have been reported as novel nanoscale contrast agents, showing great potential for biomedical applications. However, most of the GVs reported in the literature show poor contrast imaging capabilities due to their small size, especially for the in vivo condition. In this study, we isolated the rugby-ball-shaped GVs from Halobacteria NRC-1 and characterized their contrast imaging properties in vitro and in vivo. Our results showed that GVs could produce stable and strong ultrasound contrast signals in murine liver tumors using clinical diagnostic ultrasound equipment at the optimized parameters. Interestingly, we found these GVs, after systemic administration, were able to perfuse the ischemic region of a tumor where conventional lipid MBs failed, producing a 6.84-fold stronger contrast signal intensity than MBs. Immunohistochemistry staining assays revealed that the nanoscale GVs, in contrast to the microscale MBs, could penetrate through blood vessels. Thus, our study proved these biosynthesized GVs from Halobacterium NRC-1 are useful for future molecular imaging and image-guided drug delivery. [ABSTRACT FROM AUTHOR]

Drug-loaded nanoparticles have been widely used as synergists in high-intensity focused ultrasound (HIFU) tumor ablation therapy. However, these synergists have certain limitations, such as poor tumor targeting and low accumulation at the tumor site, that restrict the therapeutic efficacy of HIFU. In this study, we utilized drug-loaded nanoparticles conjugated with genetically engineered bacteria which can selectively colonize the hypoxic areas of tumor to facilitate HIFU ablation. Genetically modified Escherichia coli carrying gas vesicles (GVs- E. coli), which were gas-filled protein nanostructures, had a negatively charged surface and could specifically target into the tumor. In contrast, paclitaxel (PTX) and perfluorohexane (PFH) co-loaded cationic lipid nanoparticles (PTX-CLs) had a positively charged surface, hence, GVs- E. coli was used as a vehicle by conjugating with PTX-CLs via electrostatic adsorption and subsequently attracting more PTX-CLs to the tumor site. To improve the therapeutic efficiency of HIFU, the GVs in GVs- E. coli and PFH encapsulated in PTX-CLs could act as cavitation nuclei to enhance the HIFU cavitation effect, while PTX entrapped in PTX-CLs was released at the tumor site under HIFU irradiation, enhancing the therapeutic efficacy of HIFU and chemo-synergistic therapy. This novel combination strategy has great potential for cancer treatment. • Drug-loaded nanoparticles were electrostatically adsorbed on engineered GVs- E. coli. • GVs- E. coli can selectively colonize tumor site and generate gas vesicles to enhance the HIFU cavitation effect. • These attract more drug-loaded NPs to the tumor site to promote apoptosis. • The novel strategy actualize synergies of HIFU/chemotherapy in tumor treatment. [ABSTRACT FROM AUTHOR]

Haiyan Yang,1 Fujie Jiang,1 Xiaojuan Ji,2 Lu Wang,1 Yaotai Wang,1 Liang Zhang,3 Yu Tang,1 Disen Wang,1 Yong Luo,1 Ningshan Li,1 Qi Wang,1 Jianzhong Zou1 1State Key Laboratory of Ultrasound in Medicine and Engineering, College of Biomedical Engineering, Chongqing Medical University, Chongqing 400016, China; Chongqing Key Laboratory of Biomedical Engineering, Chongqing Medical University, Chongqing 400016, People’s Republic of China; 2Department of Ultrasound, Children’s Hospital of Chongqing Medical University, Ministry of Education Key Laboratory of Child Development and Disorders; National Clinical and Research Center of Child Health and Disorders; China International Science and Technology Cooperation Base of Child Development and Critical Disorders; Chongqing Engineering Research Center of Stem Cell Therapy, Chongqing 400016, People’s Republic of China; 3Institute of Ultrasound Imaging, The Second Affiliated Hospital of Chongqing Medical University, Chongqing 400010, People’s Republic of ChinaCorrespondence: Jianzhong ZouState Key Laboratory of Ultrasound in Medicine and Engineering, College of Biomedical Engineering, Chongqing Medical University, Chongqing, Yuzhong District 400016, People’s Republic of ChinaTel +86-13708302390Email zoujzh@cqmu.edu.cnPurpose: Cancer treatment still faces big challenges in the clinic, which is raising concerns over the world. In this study, we report the novel strategy of combing bacteriotherapy with high-intensity focused ultrasound (HIFU) therapy for more efficient breast cancer treatment.Methods: The acoustic reporter gene (ARG) was genetically engineered to be expressed successfully in Escherichia coli (E. coli) to produce the protein nanoparticles-gas vesicles (GVs). Ultrasound was utilized to visualize the GVs in E. coli. In addition, it was injected intravenously for targeted breast cancer therapy by combing the bacteriotherapy with HIFU therapy.Results: ARG expressed in E. coli can be visualized in vitro and in vivo by ultrasound. After intravenous injection, E. coli containing GVs could specifically target the tumor site, colonize consecutively in the tumor microenvironment, and it could obviously inhibit tumor growth. Meanwhile, E. coli which contained GVs could synergize HIFU therapy efficiently both in vitro and in vivo as the cavitation nuclei. Furthermore, the tumor inhibition rate in the combination therapy group could be high up to 87% compared with that in the control group.Conclusion: Our novel strategy of combing bacteriotherapy with HIFU therapy can treat breast cancers more effectively than the monotherapies, so it can be seen as a promising strategy.Keywords: acoustic reporter gene, gas vesicles, targeted cancer therapy, bacteriotherapy, high-intensity focused ultrasound

The present study aimed to use comparative genomics to explore the relationships between Frankia and actinorhizal plants using a data set made of 33 Frankia genomes. The determinants of host specificity were first explored for “Alnus-infective strains” (i.e., Frankia strains belonging to Cluster Ia). Several genes were specifically found in these strains, including an agmatine deiminase which could possibly be involved in various functions as access to nitrogen sources, nodule organogenesis or plant defense. Within “Alnus-infective strains”, Sp+ Frankia genomes were compared to Sp− genomes in order to elucidate the narrower host specificity of Sp+ strains (i.e., Sp+ strains being capable of in planta sporulation, unlike Sp− strains). A total of 88 protein families were lost in the Sp+ genomes. The lost genes were related to saprophytic life (transcriptional factors, transmembrane and secreted proteins), reinforcing the proposed status of Sp+ as obligatory symbiont. The Sp+ genomes were also characterized by a loss of genetic and functional paralogs, highlighting a reduction in functional redundancy (e.g., hup genes) or a possible loss of function related to a saprophytic lifestyle (e.g., genes involved in gas vesicle formation or recycling of nutrients).

• Review of recent ultrasound neuroimaging methods. • Review of ultrasound contrast agents used in ultrasound neuroimaging. • Review of genetically encoded acoustic biosensors. • Review of emerging biomolecular ultrasound imaging applications. Ultrasound imaging is one of the most widely used modalities in clinical practice, revealing human prenatal development but also arterial function in the adult brain. Ultrasound waves travel deep within soft biological tissues and provide information about the motion and mechanical properties of internal organs. A drawback of ultrasound imaging is its limited ability to detect molecular targets due to a lack of cell-type specific acoustic contrast. To date, this limitation has been addressed by targeting synthetic ultrasound contrast agents to molecular targets. This molecular ultrasound imaging approach has proved to be successful but is restricted to the vascular space. Here, we introduce the nascent field of biomolecular ultrasound imaging, a molecular imaging approach that relies on genetically encoded acoustic biomolecules to interface ultrasound waves with cellular processes. We review ultrasound imaging applications bridging wave physics and chemical engineering with potential for deep brain imaging. [ABSTRACT FROM AUTHOR]

Applying nanosized ultrasound contrast agents (nUCAs) in molecular imaging has received considerable attention. nUCAs have been instrumental in ultrasound molecular imaging to enhance sensitivity, identification, and quantification. nUCAs can achieve high performance in molecular imaging, which was influenced by synthetic formulations and size. This review presents an overview of nUCAs from different synthetic formulations with a discussion on imaging and detection technology. Then we also review the progress of nUCAs in preclinical application and highlight the recent challenges of nUCAs.

Our previous work developed acoustic response bacteria, which enable the precise tuning of transgene expression through ultrasound. However, it is still difficult to visualize these bacteria in order to guide the sound wave to precisely irradiate them. Here, we develop ultrasound-visible engineered bacteria and chemically modify them with doxorubicin (DOX) on their surfaces. These engineered bacteria (Ec@DIG-GVs) can produce gas vesicles (GVs), providing a real-time imaging guide for remote hyperthermia high-intensity focused ultrasound (hHIFU) to induce the expression of the interferon (IFN)-γ gene. The production of IFN-γ can kill tumor cells, induce macrophage polarization from the M2 to the M1 phenotype, and promote the maturation of dendritic cells. DOX can be released in the acidic tumor microenvironment, resulting in immunogenic cell death of tumor cells. The concurrent effects of IFN-γ and DOX activate a tumor-specific T cell response, producing the synergistic anti-tumor efficacy. Our study provides a promising strategy for bacteria-mediated tumor chemo-immunotherapy., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Archaea are prokaryotic organisms that were classified as a new domain in 1990. Archaeal cellular components and metabolites have found various applications in the pharmaceutical industry. Some archaeal lipids can be used to produce archaeosomes, a new family of liposomes that exhibit high stability to temperatures, pH and oxidative conditions. Additionally, archaeosomes can be efficient antigen carriers and adjuvants promoting humoral and cellular immune responses. Some archaea produce gas vesicles, which are nanoparticles released by the archaea that increase the buoyancy of the cells and facilitate an upward flotation in water columns. Purified gas vesicles display a great potential for bioengineering, due to their high stability, immunostimulatory properties and uptake across cell membranes. Both archaeosomes and archaeal gas vesicles are attractive tools for the development of novel drug and vaccine carriers to control various diseases. In this review we discuss the current knowledge on production, preparation methods and potential applications of archaeosomes and gas vesicles as carriers for vaccines. We give an overview of the traditional structures of these carriers and their modifications. A comparative analysis of both vaccine delivery systems, including their advantages and limitations of their use, is provided. Gas vesicle- and archaeosome-based vaccines may be powerful next-generation tools for the prevention and treatment of a wide variety of infectious and non-infectious diseases. [ABSTRACT FROM AUTHOR]

Archaea are prokaryotic organisms that were classified as a new domain in 1990. Archaeal cellular components and metabolites have found various applications in the pharmaceutical industry. Some archaeal lipids can be used to produce archaeosomes, a new family of liposomes that exhibit high stability to temperatures, pH and oxidative conditions. Additionally, archaeosomes can be efficient antigen carriers and adjuvants promoting humoral and cellular immune responses. Some archaea produce gas vesicles, which are nanoparticles released by the archaea that increase the buoyancy of the cells and facilitate an upward flotation in water columns. Purified gas vesicles display a great potential for bioengineering, due to their high stability, immunostimulatory properties and uptake across cell membranes. Both archaeosomes and archaeal gas vesicles are attractive tools for the development of novel drug and vaccine carriers to control various diseases. In this review we discuss the current knowledge on production, preparation methods and potential applications of archaeosomes and gas vesicles as carriers for vaccines. We give an overview of the traditional structures of these carriers and their modifications. A comparative analysis of both vaccine delivery systems, including their advantages and limitations of their use, is provided. Gas vesicle- and archaeosome-based vaccines may be powerful next-generation tools for the prevention and treatment of a wide variety of infectious and non-infectious diseases.

The formation of gas vesicles has been investigated in bacteria and haloarchaea for more than 50 years. These air-filled nanostructures allow cells to stay at a certain height optimal for growth in their watery environment. Several gvp genes are involved and have been studied in Halobacterium salinarum, cyanobacteria, Bacillus megaterium, and Serratia sp. ATCC39006 in more detail. GvpA and GvpC form the gas vesicle shell, and additional Gvp are required as minor structural proteins, chaperones, an ATP-hydrolyzing enzyme, or as gene regulators. We analyzed the Gvp proteins of Hbt. salinarum with respect to their protein–protein interactions, and developed a model for the formation of these nanostructures. Gas vesicles are also used in biomedical research. Since they scatter waves and produce ultrasound contrast, they could serve as novel contrast agent for ultrasound or magnetic resonance imaging. Additionally, gas vesicles were engineered as acoustic biosensors to determine enzyme activities in cells. These applications are based on modifications of the surface protein GvpC that alter the mechanical properties of the gas vesicles. In addition, gas vesicles have been decorated with GvpC proteins fused to peptides of bacterial or viral pathogens and are used as tools for vaccine development.

Gas vesicles (GVs) are cylindrical or spindle‐shaped protein nanostructures filled with air and used for flotation by various cyanobacteria, heterotrophic bacteria, and Archaea. Recently, GVs have gained interest in biotechnology applications due to their ability to serve as imaging agents and actuators for ultrasound, magnetic resonance and several optical techniques. The diameter of GVs is a crucial parameter contributing to their mechanical stability, buoyancy function and evolution in host cells, as well as their properties in imaging applications. Despite its importance, reported diameters for the same types of GV differ depending on the method used for its assessment. Here, we provide an explanation for these discrepancies and utilize electron microscopy (EM) techniques to accurately estimate the diameter of the most commonly studied types of GVs. We show that during air drying on the EM grid, GVs flatten, leading to a ~1.5‐fold increase in their apparent diameter. We demonstrate that GVs' diameter can be accurately determined by direct measurements from cryo‐EM samples or alternatively indirectly derived from widths of flat collapsed and negatively stained GVs. Our findings help explain the inconsistency in previously reported data and provide accurate methods to measure GVs dimensions. [ABSTRACT FROM AUTHOR]

Ultrasound contrast agents are valuable for diagnostic imaging and drug delivery. Generally, chemically synthesized microbubbles (MBs) are micro-sized particles. Particle size is a limiting factor for the diagnosis and treatment of many extravascular diseases. Recently, gas vesicles (GVs) from some marine bacteria and archaea have been reported as novel nanoscale contrast agents, showing great potential for biomedical applications. However, most of the GVs reported in the literature show poor contrast imaging capabilities due to their small size, especially for the in vivo condition. In this study, we isolated the rugby-ball-shaped GVs from Halobacteria NRC-1 and characterized their contrast imaging properties in vitro and in vivo. Our results showed that GVs could produce stable and strong ultrasound contrast signals in murine liver tumors using clinical diagnostic ultrasound equipment at the optimized parameters. Interestingly, we found these GVs, after systemic administration, were able to perfuse the ischemic region of a tumor where conventional lipid MBs failed, producing a 6.84-fold stronger contrast signal intensity than MBs. Immunohistochemistry staining assays revealed that the nanoscale GVs, in contrast to the microscale MBs, could penetrate through blood vessels. Thus, our study proved these biosynthesized GVs from Halobacterium NRC-1 are useful for future molecular imaging and image-guided drug delivery.

Defining the physiological traits that characterise phytoplankton involves comparison with related organisms in benthic habitats. Comparison of survival time in darkness under natural conditions requires more information. Gas vesicles and flagella as mechanisms of upward movement relative to surrounding water, allowing periodic vertical migration, are not confined to plankton, although buoyancy changes related to compositional changes of a large central vacuole may be restricted to plankton. Benthic microalgae have the same range of photosynthetic pigments as do phytoplankton; it is not clear if there are differences in the rate of regulation and acclimation of photosynthetic machinery to variations in irradiance for phytoplankton and for microphytobenthos. There are inadequate data to determine if responses to variations in frequency or magnitude of changes in the supply of inorganic carbon, nitrogen or phosphorus differ between phytoplankton and benthic microalgae. Phagophotomixotrophy and osmophotomixotrophy, occur in both phytoplankton and benthic microalgae. Further progress in identifying physiological traits specific to phytoplankton requires more experimentation on benthic microalgae that are closely related to planktonic microalgae, with attention to whether the benthic algae examined have, as far as can be determined, never been planktonic during their evolution or are derived from planktonic ancestors.

Gas vesicles mediate buoyancy-based motility in aquatic bacteria and archaea and are the only protein-based structures known to enclose a gas-filled volume. Their unique physicochemical properties and ingenious architecture rank them among the most intriguing macromolecular assemblies characterised to date. This review covers the 60-year journey in quest for a high-resolution structural model of gas vesicles, first highlighting significant strides made in establishing the detailed ultrastructure of gas vesicles through transmission electron microscopy, X-ray fibre diffraction, atomic force microscopy, and NMR spectroscopy. We then survey the recent progress in cryogenic electron microscopy studies of gas vesicles, which eventually led to a comprehensive atomic model of the mature assembly. Synthesising insight from these structures, we examine possible mechanisms of gas vesicle biogenesis and growth, presenting a testable model to guide future experimental work. We conclude by discussing future directions in the structural biology of gas vesicles, particularly considering advancements in AI-driven structure prediction., (© 2024 The Author(s).)

Isosphaera pallida (ex Woronichin 1927) Giovannoni et al. 1995 is the type species of the genus Isosphaera. The species is of interest because it was the first heterotrophic bacterium known to be phototactic, and it occupies an isolated phylogenetic position within the Planctomycetaceae. Here we describe the features of this organism, together with the complete genome sequence and annotation. This is the first complete genome sequence of a member of the genus Isosphaera and the third of a member of the family Planctomycetaceae. The 5,472,964 bp long chromosome and the 56,340 bp long plasmid with a total of 3,763 protein-coding and 60 RNA genes are part of the Genomic Encyclopedia of Bacteria and Archaea project.

SUMMARY: Oscillatoria kawamurae is an unusual freshwater cyanobacterium because of its large trichome and ambiguous gas vacuole. Because little is known about its phenotypic or genotypic characteristics, this study conducted morphological, biochemical, and genetic characterization of O. kawamurae strains isolated from Japan, Laos, and Myanmar. All strains displayed similar morphological characteristics; however some differences were observed in vegetative cell widths, trichome colors, and the distribution patterns of their gas vacuole‐like structures. The in vivo and phycobiliprotein absorption spectra revealed the two different trichome colors found in the four representative strains of O. kawamurae (Inle1, Lao7, Biwa6, and Inba3). These different trichome colors corresponded to the different ratios of phycoerythrin and phycocyanin, the two types of phycobilin pigments: 0.25 for olive‐green strain (Inle1) and 0.65–0.73 for brown‐green strains (Biwa6, Inba3, and Lao7). Cellular fatty acid compositions of the four strains were C14:0, C15:0, C16:0, C16:1c, C17:0, C18:0, C18:1c, C18:3α and C18:4, whereas two strains (Biwa6 and Inba3) lacked C17:0. Of the fatty acids, palmitic acid (C16:0) was predominant. PCR experiments using primers targeting a gas vesicle gene (gvpA) recovered gvpA fragments from all O. kawamurae strains, suggesting that this species has true gas vacuoles. The 16S rDNA sequences of all of the strains were identical regardless of their different trichome colors and/or geographic origins. Phylogenetic analyses based on the 16S rDNA sequences indicated that O. kawamurae forms a monophyletic clade with O. princeps CCALA 1115 clB1 and O. duplisecta ETS‐06. We discuss the taxonomy of O. kawamurae based on the data obtained in this study. [ABSTRACT FROM AUTHOR]

Tumor hypoxia is believed to be a factor limiting successful outcomes of oxygen-consuming cancer therapy, thereby reducing patient survival. A key strategy to overcome tumor hypoxia is to increase the prevalence of oxygen at the tumor site. Oxygen-containing microbubbles/nanobubbles have been developed to supply oxygen and enhance the effects of therapies such as radiotherapy and photodynamic therapy. However, the application of these bubbles is constrained by their poor stability, requiring major workarounds to increase their half-lives. In this study, we explore the potential of biogenic gas vesicles (GVs) as a new kind of oxygen carrier to alleviate tumor hypoxia. GVs, which are naturally formed, gas-filled, protein-shelled compartments, were modified on the surface of their protein shells by a layer of liposome. A substantial improvement of oxygen concentration was observed in hypoxic solution, in hypoxic cells, as well as in subcutaneous tumors when lipid-GVs(O 2) were added/tail-injected. Significant enhancement of tumor cell apoptosis and necrosis was also observed during photodynamic therapy (PDT) in the presence of lipid-GVs(O 2) both in vitro and in vivo. Lipid-GVs(O 2) alone induced no obvious change in cell viability in vitro or any apparent pathological abnormalities after mice were tail-injected with them. In all, lipid-GVs exhibited promising performance for intravenous gas delivery, enhanced PDT efficacy and low toxicity, a quality that may be applied to alleviate hypoxia in cancers, as well as hypoxia-related clinical treatments. The development of stable oxygen-filled micro/nanobubbles capable of delivering oxygen to tumor sites is a major hurdle to enhancing the efficacy of cancer therapy. Currently, micro/nanobubbles are limited by their instability when oxygen is encapsulated, creating a large pressure gradient and surface tension. To improve stability, we modified the surfaces of GVs, a biogenic stable nanoscale hollow structure, as a new class of oxygen carriers. Lipid-coated GVs were found to be stable in solution and effective O 2 carriers. This will overcome the limitations of coalescence, short circulation time of synthetic bubbles during application. Our surface-modified GVs demonstrated low toxicity in vitro cell in vivo , while also being able to overcome hypoxia-associated therapy resistance when combined with photodynamic therapy. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Gas vesicles (GVs) are nanosized structures (45-800 nm) and have been reported to produce non-linear contrast signals, making them an attractive agent for molecular targeting of tumors. One barrier to their use for pre-clinical oncology studies is rapid uptake into the reticuloendothelial system (RES) and consequent rapid decrease in contrast signal after infusion ends and low signal on reperfusion after a bubble burst sequence. The purpose of this study was to examine suppression of the RES and surface modification of GVs to prolong contrast circulation in tumors for ultrasound imaging. Ultrasound imaging to measure dynamics of contrast signal intensity in tumor models was carried out using a 21-MHz high-frequency array transducer with the Vevo 2100 ultrasound system. The non-linear contrast signal from intravenously injected GVs compared with peak enhancement was measured during contrast wash-out and on reperfusion after a contrast burst sequence. Disrupting the RES by saturating the macrophage population or chemically inhibiting the Kupffer cell population with gadolinium or Intralipid preserves 62%-88% of GVs' contrast enhancement relative to peak during the wash-out phase and 32%-56% on reperfusion compared with 38% and 14%, respectively, for no disruption of the RES, indicating longer circulation of GVs in the tumor. Additionally, coating the GVs with 2-, 5- or 10-kDa polyethylene glycol (PEG) chains resulted in >70% contrast signal retention in the tumors during wash-out and, for 5- or 10-kDa PEG chains, a return to >45% of peak contrast signal on reperfusion. These findings indicate that GVs can be used as a contrast agent for tumor imaging and that disruption of the RES improved recirculation and maintained contrast enhancement caused by GVs in the tumors. [ABSTRACT FROM AUTHOR]

Use of gas vesicles (GVs) as biosynthetic ultrasound molecular imaging (UMI) probes has become a hot topic of research in recent years owing to their advantages of high stability, low risk of toxicity, genetic engineering characterization, easy post-modification, and drug-loading potential. Exploration of natural GV biosynthetic resources and their corresponding biosynthetic elements for various ultrasonic diagnosis and treatment needs to be developed in this field. In this study, we utilized the sequenced cyanobacteria resources preserved in the Freshwater Algae Culture Collection at the Institute of Hydrobiology (FACHB) to screen seed cells and corresponding synthetic elements for biosynthesis of UMI probes. GV operons from the genomes of 158 strains of cyanobacteria were analyzed to identify their natural GV biosynthetic elements. Based on the ultrasound screening method (VINNO D860LAB, 2D transducer X6-16L, 50 % output power mode, MI: 1.116), 57 seed resources with biosynthetic UMI probe potential from 10 genera were selected from 158 strains of cyanobacteria, corresponding to 28 types of effective biosynthetic elements. These results provide a theoretical basis for future mass production of customized GVs in chassis cells and their application in UMI. [Display omitted] • A rapid screening method for biosynthetic UMI probes seed cells was established. • 57 cyanobacteria seed cells were identified with biosynthetic UMI probe potential. • 28 types of biosynthetic elements were identified to produce GVs in 57 seed cells. [ABSTRACT FROM AUTHOR]

Cyanobacterial bloom is one of the most urgent global environmental issues, which eventually could threaten human health and safety. Sonication treatment (ST) is a potential effective method to control cyanobacteria blooms in the field. Currently, the bottleneck of extensive application of ST is the difficulty to estimate the ST effect on the cyanobacterial cells and then determine suitable ST times in the field. In this study, cyanobacterial Microcystis samples sonicated at different times were first measured by a spectrophotometer to calculate the removal efficiency of Microcystis cells. Additionally, they were observed by TEM to reveal the intracellular structure changes of the cells. Then the samples were measured by an experimental setup based on polarized light scattering to measure the polarization parameters. Experimental results indicated that the polarization parameters can effectively characterize the intracellular structural changes of Microcystis cells with different ST times, which is quite consistent with the results for removal efficiency and TEM images. Further, the optimal ST time can be inferred by the polarization parameters. These results demonstrate that polarized light scattering can be a potentially powerful tool to explore suitable times for sonication treatment of cyanobacteria blooms.

Sonogenetics is an emerging approach that harnesses ultrasound for the manipulation of genetically modified cells. The great penetrability of ultrasound waves enables the non-invasive application of external stimuli to deep tissues, particularly advantageous for brain stimulation. Genetically encoded ultrasound mediators, a set of proteins that respond to ultrasound-induced bio-effects, play a critical role in determining the effectiveness and applications of sonogenetics. In this context, we will provide an overview of these ultrasound-responsive mediators, delve into the molecular mechanisms governing their response to ultrasound stimulation, and summarize their applications in neuromodulation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Wang, Phan, Kao, Yeh and Lin.)

Gas vesicles (GVs) are genetically encoded, air-filled protein nanostructures of broad interest for biomedical research and clinical applications, acting as imaging and therapeutic agents for ultrasound, magnetic resonance, and optical techniques. However, the biomedical applications of GVs as systemically injectable nanomaterials have been hindered by a lack of understanding of GVs' interactions with blood components, which can significantly impact in vivo behavior. Here, we investigate the dynamics of GVs in the bloodstream using a combination of ultrasound and optical imaging, surface functionalization, flow cytometry, and mass spectrometry. We find that erythrocytes and serum proteins bind to GVs and shape their acoustic response, circulation time, and immunogenicity. We show that by modifying the GV surface we can alter these interactions and thereby modify GVs' in vivo performance. These results provide critical insights for the development of GVs as agents for nanomedicine.

Gas vesicles (GVs) are gas-filled protein nanostructures that can regulate the buoyancy of microorganisms such as cyanobacteria and archaea. Recent studies have shown that GVs have the potential to be used as ultrasound molecular imaging probes in disease diagnosis and treatment. However, the mechanism of the inflation and deflation of GVs remains unclear, which hampers the preservation of GVs and gas replacement. In the present study, the environmental pH value was found to be an important factor in regulating the inflation and deflation of GVs. It can not only regulate the inflation and deflation of GVs in vivo to make Microcystis sp. cells present distinct levitation state, but also regulate the inflation and deflation of purified GVs in vitro , and the regulation process is reversible. Our results may provide a technical support for the large-scale production and preservation of biosynthetic ultrasound molecular imaging probes, especially for gas replacement to meet different diagnostic and therapeutic needs, and would facilitate the application of biosynthetic ultrasound molecular imaging probes.