Bacterial System Research Articles

Phenotypic and genotypic analysis of drug resistance in M. tuberculosis isolates in Gansu, China.

Tuberculosis has posed a serious threat to human health. It is imperative to investigate the geographic prevalence of tuberculosis and medication resistance, as this information is essential for informing strategies for its prevention and treatment. Drug resistance was identified using a proportion method. Drug-resistant genes and pathways were predicted using whole genome sequencing. The drug resistance range of bedaquiline was identified using the microporous plate two-fold dilution method, and drug resistance genes were studied using sequencing. The study revealed that 19.99% of the tuberculosis cases had multidrug resistance. The genes of M. tuberculosis are predominantly involved in the synthesis of ABC transporters, two-component systems, and bacterial secretion systems, as well as in energy production and conversion, and lipid transport and metabolism. The genes encode for 82.45% of carbohydrate-related enzymes such as glycoside hydrolases, glycosyl transferases, and carbohydrate esterases. The minimum inhibitory concentration (MIC) of bedaquiline against clinical strains was approximately 0.06 μg/mL, with identified mutations in drug-resistant genes Rv0678, atpE, and pepQ, specifically V152A, P62A, and T222N, respectively. The multidrug resistance tuberculosis development was attributed to the strong medication resistance exhibited. It was concluded that tuberculosis had presented a high level of drug resistance. Phenotypic resistance was related to genes, existing potential genetic resistance in M. tuberculosis. Bedaquiline was found to possess effective antibacterial properties against M. tuberculosis.

Purification of Recombinant N-terminal Histidine-Tagged Arabidopsis thaliana Phosphoglycolate Phosphatase 1, Glycolate Oxidase 1 and 2, and Hydroxypyruvate Reductase 1.

To measure the kinetic properties of photorespiratory enzymes, it is necessary to work with purified proteins. Protocols to purify photorespiratory enzymes from leaves of various plant species require several time-consuming steps. It is now possible to produce large quantities of recombinant proteins in bacterial cells. They can be rapidly purified as histidine-tagged recombinant proteins by immobilized metal affinity chromatography using Ni2+-NTA-agarose. This chapter describes protocols to purify several Arabidopsis thaliana His-tagged recombinant photorespiratory enzymes (phosphoglycolate phosphatase, glycolate oxidase, and hydroxypyruvate reductase) from Escherichia coli cell cultures using two bacterial strain-plasmid systems: BL21(DE3)-pET and LMG194-pBAD.

Protein degradation in bacteria: focus on the ClpP protease

Proteins in the cells are born (synthesized), work, and die (decomposed). In the life of a protein, its birth is obviously important, but how it dies is equally important in living organisms. Proteases secreted into the outside of cells are used to decompose the external proteins and the degradation products are taken as the nutrients. On the other hand, there are also proteases that decompose unnecessary or harmful proteins which are generated in the cells. In eukaryotes, a large enzyme complex called the proteasome is primarily responsible for degradation of such proteins. Bacteria, which are prokaryotes, have a similar system as the proteasome. We would like to explain the bacterial degradation system of proteins or the death of proteins, which is performed by ATP-dependent protease Clp, with a particular focus on the ClpXP complex, and with an aspect as a target for antibiotics against bacteria.

Polyaniline nanofiber: an excellent anode material for microbial fuel cells.

Sluggish electron transfer from the bacterial metabolic system to the electrode is a critical issue in microbial fuel cell (MFC) research. However, a number of strategies have already been demonstrated for the improved performance of MFCs through the chemical or electrochemical manipulation of the anode. In this study, a new anode fabrication technique was introduced with polyaniline nanofibers (PANInf) to increase the surface area of the anode in a three-dimensional pattern. A large number of bacteria were anchored to the high surface area anode through the electrostatic interaction between positively charged anode surface and negatively charged bacteria cell wall. An improved conductive nature also plays an important role in accelerating the electron transfer process, yielding a current density of 0.87 mA cm-2, which is almost a 73% increase from that of the PANI anode (0.503 mA cm-2). The maximum power density with a PANInf-modified anode was 1091 ± 5% mW m-2, which is 40% higher than that of the PANI-modified anode (777 ± 5% mW m-2). Impedance spectroscopic study shows that PANInf modification reasonably reduces the charge transfer resistance, leading to faster electron transfer kinetics.

Unique Behavior of Bacterially Expressed Rat Carnitine Palmitoyltransferase 2 and Its Catalytic Activity.

Mammalian type 2 carnitine parmitoyltransferase (EC 2.3.1.21), abbreviated as CPT2, is an enzyme involved in the translocation of fatty acid into the mitochondrial matrix space, and catalyzes the reaction acylcarnitine + CoA = acyl-CoA + carnitine. When rat CPT2 was expressed in Escherichia coli, its behavior was dependent on the presence or absence of i) its mitochondrial localization sequence and ii) a short amino acid sequence thought to anchor it to the mitochondrial inner membrane: CPT2 containing both sequences behaved as a hydrophobic protein, while recombinant CPT2 lacking both regions behaved as a water soluble protein; if only one region was present, the resultant proteins were observed in both fractions. Because relatively few protein species could be obtained from bacterial lysates as insoluble pellets under the experimental conditions used, selective enrichment of recombinant CPT2 protein containing both hydrophobic sequences was easily achieved. Furthermore, when CPT2 enriched in insoluble fraction was resuspended in an appropriate medium, it showed catalytic activity typical of CPT2: it was completely suppressed by the CPT2 inhibitor, ST1326, but not by the CPT1 inhibitor, malonyl-CoA. Therefore, we conclude that the bacterial expression system is an effective tool for characterization studies of mammalian CPT2.

Screening of insect immune suppressors using a recombinant phospholipase A2 of a lepidopteran insect.

Phospholipase A2 (PLA2 ) catalyzes phospholipids at the sn-2 position to release free fatty acids, including arachidonic acid (AA) or its precursor. The free AA is then oxygenated into different eicosanoids, which mediate the diverse physiological processes in insects. Any inhibition of the PLA2 catalysis would give rise to serious malfunctioning in insect growth and development. An onion moth, Acrolepiopsis sapporensis, encodes four different PLA2 genes (As-PLA2 A-As-PLA2 D), in which As-PLA2 A is dominantly expressed at all developmental stages and in different larval tissues. RNA interference of the As-PLA2 A expression significantly reduced the PLA2 activity of A. sapporensis, which suffered from immunosuppression. A recombinant As-PLA2 A protein was purified from a bacterial expression system, which exhibited a typical Michaelis-Menten kinetics and hence susceptible to a specific inhibitor to sPLA2 and dithiothreitol. A total of 19 bacterial metabolites derived from Xenorhabdus and Photorhabdus were screened against the recombinant As-PLA2 A. Five potent metabolites were highly inhibitory and followed a competitive enzyme inhibition. These five inhibitors suppressed the immune responses of A. sapporensis by inhibiting hemocyte-spreading behavior and phenoloxidase activity. However, an addition of AA could significantly rescue the immunosuppression induced by the selected inhibitors. These studies suggest that the recombinant As-PLA2 A protein can be applied for high-throughput screening of insect immunosuppressive compounds.

Identification of novel small molecule inhibitors of twin arginine translocation (Tat) pathway and their effect on the control of Campylobacter jejuni in chickens.

Control of Campylobacter from farm to fork is challenging due to the frequent emergence of antimicrobial-resistant isolates. Furthermore, poultry production systems are known reservoirs of Campylobacter. The twin-arginine translocation (Tat) pathway is a crucial bacterial secretion system that allows Campylobacter to colonize the host intestinal tract by using formate as the main source of energy. However, Tat pathway is also a major contributing factor for resistance to copper sulfate (CuSO4). Since mammals and chickens do not have proteins or receptors that are homologous to bacterial Tat proteins, identification of small molecule (SM) inhibitors targeting the Tat system would allow the development of safe and effective control methods to mitigate Campylobacter in infected or colonized hosts in both pre-harvest and post-harvest. In this study, we screened 11 commercial libraries (n = 50,917 SM) for increased susceptibility to CuSO4 (1 mM) in C. jejuni 81-176, a human isolate which is widely studied. Furthermore, we evaluated 177 SM hits (2.5 μg/mL and above) that increased the susceptibility to CuSO4 for the inhibition of formate dehydrogenase (Fdh) activity, a Tat-dependent substrate. Eight Tat-dependent inhibitors (T1-T8) were selected for further studies. These selected eight Tat inhibitors cleared all tested Campylobacter strains (n = 12) at >10 ng/mL in the presence of 0.5 mM CuSO4in vitro. These selected SMs were non-toxic to colon epithelial (Caco-2) cells when treated with 50 μg/mL for 24 h and completely cleared intracellular C. jejuni cells when treated with 0.63 μg/mL of SM for 24 h in the presence of 0.5 mM of CuSO4. Furthermore, 3 and 5-week-old chicks treated with SM candidates for 5 days had significantly decreased cecal colonization (up to 1.2 log; p < 0.01) with minimal disruption of microbiota. In silico analyses predicted that T7 has better drug-like properties than T2 inhibitor and might target a key amino acid residue (glutamine 165), which is located in the hydrophobic core of TatC protein. Thus, we have identified novel SM inhibitors of the Tat pathway, which represent a potential strategy to control C. jejuni spread on farms.

Structural Variations and Rearrangements in Bacterial Type II Toxin-Antitoxin Systems.

Bacteria encode a wide range of survival and immunity systems, including CRISPR-Cas, restriction-modification systems, and toxin-antitoxin systems involved in defence against bacteriophages, as well as survival during challenging growth conditions or exposure to antibiotics. Toxin-antitoxin (TA) systems are small two- or three-gene cassettes consisting of a metabolic regulator (the "toxin") and its associated antidote (the "antitoxin"), which also often functions as a transcriptional regulator. TA systems are widespread in the genomes of pathogens but are also present in commensal bacterial species and on plasmids. For mobile elements such as plasmids, TA systems play a role in maintenance, and increasing evidence now points to roles of chromosomal toxin-antitoxin systems in anti-phage defence. Moreover, the widespread occurrence of toxin-antitoxin systems in the genomes of pathogens has been suggested to relate to survival during host infection as well as in persistence during antibiotic treatment. Upon repeated exposure to antibiotics, TA systems have been shown to acquire point mutations as well as more dramatic rearrangements such as in-frame deletions with potential relevance for bacterial survival and pathogenesis. In this review, we present an overview of the known functional and structural consequences of mutations and rearrangements arising in bacterial toxin-antitoxin systems and discuss their relevance for survival and persistence of pathogenic species.

Expression, Purification, and Cryo-EM Structural Analysis of an Outer Membrane Secretin Channel.

Secretin proteins form pores in the outer membranes of Gram-negative bacteria, and as such provide a means of transporting a wide variety of molecules out of or into the cell. They are important components of several different bacterial secretion systems, surface filament assembly machineries, and virus assembly complexes. Despite accommodating a diverse assortment of molecules, including virulence factors, folded proteins, and whole viruses, the secretin family of proteins is highly conserved, particularly in their membrane-embedded β-barrel domain. We describe here a protocol for the expression, purification and cryo-EM structural determination of the pIV secretin from the Ff family of filamentous bacteriophages.

Cost-effectiveness of 20-valent pneumococcal conjugate vaccine in US infants

BackgroundAs of June 2023, two pneumococcal conjugate vaccines, 20- (PCV20) and 15- (PCV15) valent formulations, are recommended for US infants under a 3 + 1 schedule. This study evaluated the health and economic impact of vaccinating US infants with a new expanded valency PCV20 formulation. MethodsA population-based, multi cohort, decision-analytic Markov model was developed to estimate the public health impact and cost-effectiveness of PCV20 from both societal and healthcare system perspectives over 10 years. Epidemiological data were based on published studies and unpublished Active Bacterial Core Surveillance System (ABCs) data. Vaccine effectiveness was based on PCV13 effectiveness and PCV7 efficacy studies. Indirect impact was based on observational studies. Costs and disutilities were based on published data. PCV20 was compared to both PCV13 and PCV15 in separate scenarios. ResultsReplacing PCV13 with PCV20 in infants has the potential to avert over 55,000 invasive pneumococcal disease (IPD) cases, 2.5 million pneumonia cases, 5.4 million otitis media (OM) cases, and 19,000 deaths across all ages over a 10-year time horizon, corresponding to net gains of 515,000 life years and 271,000 QALYs. Acquisition costs of PCV20 were offset by monetary savings from averted cases resulting in net savings of $20.6 billion. The same trend was observed when comparing PCV20 versus PCV15, with a net gain of 146,000 QALYs and $9.9 billion in net savings. A large proportion of the avoided costs and cases were attributable to indirect effects in unvaccinated adults and elderly. From a health-care perspective, PCV20 was also the dominant strategy compared to both PCV13 and PCV15. ConclusionsInfant vaccination with PCV20 is estimated to further reduce pneumococcal disease and associated healthcare system and societal costs compared to both PCV13 and PCV15.

Use of paired Cas9-NG nickase and truncated sgRNAs for single-nucleotide microbial genome editing.

The paired nickases approach, which utilizes clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated proteins (Cas) nickase and dual guide RNA, has the advantage of reducing off-target effects by being able to double the target sequence. In this study, our research utilized the Cas9-NG nickase variant to minimize PAM sequence constraints, enabling the generation of paired nicks at desired genomic loci. We performed a systematic investigation into the formation sites for double nicks and the design of donor DNA within a bacterial model system. Although we successfully identified the conditions necessary for the effective formation of double nicks in vivo, achieving single-nucleotide level editing directly at the target sites in the genome proved challenging. Nonetheless, our experiments revealed that efficient editing at the single-nucleotide level was achievable on target DNA sequences that are hybridized with 5'-end-truncated dual single-guide RNAs (sgRNAs). Our findings contribute to a deeper understanding of the paired nickases approach, offering a single-mismatch intolerance design strategy for accurate nucleotide editing. This strategy not only enhances the precision of genome editing but also marks a significant step forward in the development of nickase-derived genome editing technologies.

A comprehensive study on the risk factors and pathogen analysis of postoperative wound infections following caesarean section procedures.

Postoperative wound infections (PWIs), a subtype of surgical site infections, are a significant concern for patients undergoing caesarean sections (C-sections). Understanding risk factors and pathogen profiles can greatly assist in early diagnosis and effective treatment. This study aimed to identify risk factors and analyse the pathogenic landscape contributing to PWIs in C-sections. A nested case-control study was carried out, utilising stringent criteria for case selection and control matching. Diagnostic criteria for surgical site infections included both clinical and microbiological parameters. Risk variables examined included patient age, Body Mass Index, duration of surgery and several other clinical indicators. Microbiological analysis was performed using the BD Phoenix-100 Automated Bacterial Identification System. Statistical analyses were conducted using SPSS version 26.0, and risk factors were evaluated through both univariate and multivariate analyses. A total of 50 patients, aged between 20 and 45 years (mean age 26.3 ± 5.6), developed PWIs following C-sections. The study revealed a temporal distribution and various clinical indicators of PWIs, including elevated white blood cell count and C-reactive protein levels. Gram-negative bacteria were found to be more prevalent at 57.4%. Notable pathogens included Pseudomonas aeruginosa and Acinetobacter baumannii. Antimicrobial resistance patterns were also identified, highlighting the need for a targeted antibiotic approach. Increased infection risks were linked to lack of prophylactic antibiotics, absence of preoperative povidone-iodine antisepsis, operations over an hour, anaemia, amniotic fluid contamination, diabetes, GTI, premature rupture of membranes and white blood cells counts above 10 × 109 /L. The study provides critical insights into the risk factors and microbial agents contributing to PWIs following C-sections. Our findings emphasise the importance of early diagnosis through clinical and laboratory parameters, as well as the need for constant surveillance and reassessment of antibiotic stewardship programs.

Recent Advances in Genetically Engineered Microorganisms and their Risks: A Review

Genetically engineered microorganisms have applications in various domains, such as agriculture, bioscience, healthcare, life sciences, and research. The novel methods of the system Clustered Regularly Interspaced Short Palindromic Repeats associated with protein 9, which originates from archaeal and bacterial immune systems and allows significant improvements to modified strains of microorganisms, represented a major innovation in industrial biotechnology. The rapid advancement of genetically engineered microorganisms has shown potential for bioremediation, food enzyme production, probiotics, and pesticides. Recently, engineered microbes have been used in several industries, like dairy, pharmaceuticals, biotech, and agrochemicals. Modified microorganisms used as biosensors are improved with reporter genes that induce their expression depending on the nature and concentration of the compound of interest to monitor environmental pollution. Genetically engineered microorganisms have been considered a threat to the environment, animals, and human health. Insertion of a single gene into different cells can result in diverse outcomes, and the general pattern of gene expression can be changed. More advanced and better techniques should be developed and applied in the genetic engineering of microbes to minimize risks.

Biophysical characterization of human-cell-expressed, full-length κI O18/O8, AL-09, λ6a, and Wil immunoglobulin light chains

Immunoglobulin light chain (AL) amyloidosis involves the deposition of insoluble monoclonal AL protein fibrils in the extracellular space of different organs leading to dysfunction and death. Development of methods to efficiently express and purify AL proteins with acceptable standards of homogeneity and structural integrity has become critical to understand the in vitro and in vivo aspects of AL protein aggregation, and thus the disease progression. In this study, we report the biophysical characterization of His-tagged and untagged versions of AL full-length (FL) κI and λ6 subgroup proteins and their mutants expressed from the Expi293F human cell line. We used an array of biophysical and biochemical methods to analyze the structure and stability of the monomers, oligomerization states, and thermodynamic characteristics of the purified FL proteins and how they compare with the bacterially expressed FL proteins. Our results demonstrate that the tagged and untagged versions of FL proteins have comparable stability to proteins expressed in bacterial cells but exhibit multiple unfolding transitions and reversibility. Non-reducing SDS-PAGE and analytical ultracentrifugation analysis showed presence of monomers and dimers, with an insignificant amount of higher-order oligomers, in the purified fraction of all proteins. Overall, the FL proteins were expressed with sufficient yields for biophysical studies and can replace bacterial expression systems.

Improving phage therapy by evasion of phage resistance mechanisms.

Antibiotic failure is one of the most worrisome threats to global health. Among the new therapeutic efforts that are being explored, the use of bacteriophages (viruses that kill bacteria), also known as 'phages', is being extensively studied as a strategy to target bacterial pathogens. However, one of the main drawbacks of phage therapy is the plethora of defence mechanisms that bacteria use to defend themselves against phages. This review aims to summarize the therapeutic approaches that are being evaluated to overcome the bacterial defence systems, including the most innovative therapeutic approaches applied: circumvention of phage receptor mutations; modification of prophages; targeting of CRISPR-Cas systems and the biofilm matrix; engineering of safer and more efficacious phages; and inhibition of the anti-persister strategies used by bacteria.

Regulation of PhoB on biofilm formation and hemolysin gene hlyA and ciaR of Streptococcus agalactiae

PhoB is a response regulator protein that plays a key role in the PhoBR two-component signal transduction system. In this study, we used transcriptome and proteomics techniques to evaluate the detect the gene network regulated by PhoB of Streptococcus agalactiae. The results showed that expression of biofilm formation and virulence-related genes were changed after phoB deficiency. Crystal violet and CLSM assay confirmed that the deletion of the phoB increased the thickness of S. agalactiae biofilm. The results of lacZ reporter and the bacterial one-hybridization method showed that PhoB could directly bind to the promoter regions of hemolysin A and ciaR genes but not to the promoter regions of cylE and hemolysin III. Through the construction of an 18-base pair deoxyribose nucleic acid (DNA) random fragment library and the bacterial one-hybridization system, it was found that the conservative sequence of PhoB binding was TTGGAGAA(G/T). Our research has uncovered the virulence potential of the PhoBR two-component system of S. agalactiae. The findings of this study provide the theoretical foundation for in-depth research on the pathogenic mechanism of S. agalactiae.

Human super antibody to viral RNA-dependent RNA polymerase produced by a modified Sortase self-cleave-bacteria surface display system

BackgroundRNA-dependent RNA polymerase (RdRp) is a good target of anti-RNA virus agents; not only it is pivotal for the RNA virus replication cycle and highly conserved among RNA viruses across different families, but also lacks human homolog. Recently, human single-chain antibody (HuscFv) that bound to thumb domain of hepatitis C virus (HCV) RNA-dependent RNA polymerase (functionalized NS5B protein) was produced and engineered into cell-penetrating antibody (super antibody) in the form of cell-penetrating peptide (penetratin, PEN)-linked HuscFv (PEN-HuscFv34). The super antibody was produced and purified from inclusion body (IB) of a pen-huscfv34-vector-transformed Escherichia coli. The super antibody inhibited replication of alpha- and beta- coronaviruses, flaviviruses, and picornaviruses that were tested (broadly effective); thus, it has high potential for developing further towards a pan-anti-RNA virus agent. However, production, purification, and refolding of the super antibody molecules from the bacterial IB are laborious and hurdles to large-scale production. Therefore, in this study, Sortase-self-cleave method and bacteria surface display system were combined and modified for the super antibody production.Methods and resultsBL21 (DE3) ΔA E. coli, a strain lacking predominant outer membrane protein (OmpA) and ion and OmpT proteases, that displayed a membrane-anchored fusion protein, i.e., chimeric lipoprotein (Lpp′)-OmpA′, SUMO, Sortase protease, Sortase cleavage site (LPET↓G) and PEN-HuscFv34-6× His was generated. The soluble PEN-HuscFv34-6× His with glycine at the N-terminus could be released from the E. coli surface, simply by incubating the bacterial cells in a Sortase-cleavage buffer. After centrifugation, the G-PEN-HuscFv34-6× His could be purified from the supernatant. The purified G-PEN-HuscFv34-6× retained original cell-penetrating ability (being super antibody) and the broadly effective anti-RNA virus activity of the original IB-derived-PEN-HuscFv34.ConclusionThe functionalized super antibody to RNA virus RdRp was successfully produced by using combined Sortase self-cleave and bacterial surface display systems with modification. The display system is suitable for downstream processing in a large-scale production of the super antibody. It is applicable also for production of other recombinant proteins in soluble free-folding form.

Role of Pre-Farrow Natural Planned Exposure of Gilts in Shaping the Passive Antibody Response to Rotavirus A in Piglets.

Natural planned exposure (NPE) remains one of the most common methods in swine herds to boost lactogenic immunity against rotaviruses. However, the efficacy of NPE protocols in generating lactogenic immunity has not been investigated before. A longitudinal study was conducted to investigate the dynamics of genotype-specific antibody responses to different doses (3, 2 and 1) of Rotavirus A (RVA) NPE (genotypes G4, G5, P[7] and P[23]) in gilts and the transfer of lactogenic immunity to their piglets. Group 1 gilts received three doses of NPE at 5, 4 and 3 weeks pre-farrow (WPF), group 2 received two doses at 5 and 3 WPF, group 3 received one dose at 5 WPF, and group 4 received no NPE (control group). VP7 (G4 and G5) and truncated VP4* (P[7] and P[23]) antigens of RVA were expressed in mammalian and bacterial expression systems, respectively, and used to optimize indirect ELISAs to determine antibody levels against RVA in gilts and piglets. In day-0 colostrum samples, group 1 had significantly higher IgG titers compared to the control group for all four antigens, and either significantly or numerically higher IgG titers than groups 2 and 3. Group 1 also had significantly higher colostrum IgA levels than the control group for all antigens (except G4), and either significantly or numerically higher IgA levels compared to groups 2 and 3. In piglet serum, group 1 piglets had higher IgG titers for all four antigens at day 0 than the other groups. Importantly, RVA NPE stimulated antibodies in all groups regardless of the treatment doses and prevented G4, G5, P[7] and P[23] RVA fecal shedding prior to weaning in piglets in the absence of viral challenge. The G11 and P[34] RVA genotypes detected from pre-weaning piglets differed at multiple amino acid positions with parent NPE strains. In conclusion, the results of this study suggest that the group 1 NPE regimen (three doses of NPE) resulted in the highest anti-RVA antibody (IgG and IgA) levels in the colostrum/milk, and the highest IgG levels in piglet serum.

Influence of Light Irradiation on Nitrification in Microalgal–Bacterial Systems for Treating Wastewater

The use of bacterial and microalgal consortia to remove nitrogen from wastewater has garnered attention as a potential alternative to conventional systems. This approach not only reduces energy consumption but also aids in nutrient recovery. Light is essential for algae photosynthesis; however, nitrifying bacteria are also influenced by light radiation. This mini-review summarizes the current knowledge concerning photoinhibition, the light stimulation of ammonia-oxidizing bacteria (AOB), resistance to light radiation, the implementation of microalgal–bacterial systems, and the possible mechanisms involved. Nitrosomonadaceae AOB and Nitrospiraceae nitrite-oxidizing bacteria (NOB) often coexist in a microalgal–bacterial system. Studies have suggested that AOB can tolerate light radiation at 200 μmol m−2·s−1 in microalgal–bacterial systems, whereas NOB are almost completely suppressed, which can result in partial nitrification in the bioreactor. An appropriate light level can stimulate AOB growth in microalgal–bacterial granular reactors and may improve algae metabolic activity. Granular sludges or artificial “light-shielding hydrogel” could effectively protect nitrifying bacteria from light intensities up to 1600 μmol m−2·s−1 in wastewater treatment reactors. Microalgal–bacterial systems along with the associated “algal shading effect” have been widely used in pond aquaculture. This approach minimizes the need for costly mechanical aeration through photo-oxygenation and facilitates nutrient recovery by filter-feeding fish.

Recent developments in bioprocessing of recombinant antibody fragments

Biotechnological and biomedical applications of antibodies have been on a steady rise since the 1980s. As unique and highly specific bioreagents, monoclonal antibodies (mAbs) have been widely exploited and approved as therapeutic agents. However, the use of mAbs has limitations for therapeutic applications. Antibody fragments (AbFs) with preserved antigen-binding sites have a significant potential to overcome the disadvantages of conventional mAbs, such as heterogeneous tissue distribution after systemic administration, especially in solid tumors, and Fc-mediated bystander activation of the immune system. AbFs possess better biodistribution coefficient due to lower molecular weight. They preserve the functional features of mAbs, such as antigen specificity and binding, while at the same time, ensuring much better tissue penetration. An additional benefit of AbFs is the possibility of their production in bacterial and yeast cells due to the small size, more robust structure, and lack of posttranslational modifications. In this review, we described current approaches to the AbF production with recent examples of AbF synthesis in bacterial and yeast expression systems and methods for the production optimization.