Biology subjects

Makarova, K. S.

Publications and source records attributed to Makarova, K. S..

At least 19 recordsLinked to original sources

bioRxiv2026

Hawaiian Geothermal Fumaroles Contain Diverse and Novel Viruses

Microbial communities of geothermal habitats are central to understanding the evolution of life on Earth. Metagenomics has provided insight into the role of viruses in shaping microbial diversity of complex environments. However, identification of novel viruses is constrained by lack of marker genes and low nucleotide similarities between related viral taxa. While microbial and viral diversity have been explored in terrestrial hot springs and hydrothermal vent systems, other volcanic features remain underexplored. Fumaroles (steam vents) are geothermal features that heat groundwater with magma, releasing steam and volcanic gases such as CO2 and H2S. Comparatively physicochemically dynamic to hot springs, fumarole temperatures and gas emissions rapidly fluctuate with volcanic activity. Here, we describe viruses identified metagenomically from microbial mats hosted near basaltic fumaroles on the Big Island of Hawaii. To our knowledge, this is the first systematic survey of fumarole viruses. Our utilization of a sensitive profile-based approach for identification reveals high viral diversity in fumaroles, resulting in estimation of two undescribed order-level clades of Caudoviricetes (tailed phages). Viral metabolic genes provide evidence of viral-mediated adaptation of microbes to fumarole conditions. We describe patterns of viral diversity that diverge from the Bank model of viral ecology, hinting at viral dispersal between biofilms and high viral richness and evenness. Lastly, we provide a description of the first terrestrial geothermal environment dominated by Microviridae, previously only described in viral communities of deep ocean hydrothermal vents. This study offers important findings for exploration of viral ecology in extreme environments.

microbiology↗

bioRxiv2026

Diverse bacterial pattern recognition receptors sense the conserved phage proteome

Recognition of foreign molecules inside cells is critical for immunity across all domains of life. Proteins of the STAND NTPase superfamily1,2, including eukaryotic NOD-like receptors (NLRs), play a central role in this process3,4. In bacteria and archaea, although several STAND families sense phage proteins5-9, their functional diversity remains largely unexplored. We conducted a systematic phylogenetic analysis of prokaryotic STAND NTPases and identified at least 90 structurally distinct families associated with antiviral defense. We first show that the uncharacterized Avs7 family recognizes the major capsid protein (MCP) of tailed phages. Three cryo-EM structures of Salmonella enterica Avs7 reveal an asymmetric, butterfly-shaped tetramer that assembles stepwise via large, MCP-induced conformational changes, incorporating bacterial elongation factor Tu (EF-Tu) as a structural component that enhances defense. Using genetic screens with a library of 687 phage genes, we further show that 13 additional STAND families sense 13 conserved phage proteins, encompassing most of the core structural and replicative components of tailed phages. These include two distinct MCP-sensing families--Avs8 (PD-{lambda}-4) and Avs10 (Erebus/Hypnos/bNACHT64)--and 11 others (Avs11-21) recognizing the portal, portal adaptor, tail nozzle, head-tail connector, tail terminator, tail tube protein, tail assembly chaperone, tape measure protein, DNA polymerase, helicase/RecA-type ATPase, and single-stranded DNA annealing protein, respectively. Together, our findings highlight structurebased pattern recognition and host factor repurposing as fundamental strategies of bacterial immunity.

molecular biology↗

bioRxiv2025

YprA family helicases provide the missing link between diverse prokaryotic immune systems

Bacteria and archaea possess an enormous variety of antivirus immune systems that often share homologous proteins and domains, some of which contribute to diverse defense strategies. YprA family helicases are central to widespread defense systems DISARM, Dpd, and Druantia. Here, through comprehensive phylogenetic and structural prediction analysis of the YprA family, we identify several major, previously unrecognized clades, with unique signatures of domain architecture and associations with other genes. Each YprA family clade defines a distinct class of defense systems, which we denote ARMADA (disARM-related Antiviral Defense Array), BRIGADE (Base hypermodification and Restriction Involving Genes encoding ARMADA-like and Dpd-like Effectors), or TALON (TOTE-like and ARMADA-Like Operon with Nuclease). In addition to the YprA-like helicase, ARMADA systems share two more proteins with DISARM. However, ARMADA YprA homologs are most similar to those of Druantia, suggesting ARMADA is a missing link connecting DISARM and Druantia. We show experimentally that ARMADA protects bacteria against a broad range of phages via a direct, non-abortive mechanism. We also discovered multiple families of satellite phage-like mobile genetic elements that often carry both ARMADA and Druantia Type III systems and show that these can provide synergistic resistance against diverse phages.

microbiology↗

bioRxiv2025

END nucleases: Antiphage defense systems targeting multiple hypermodified phage genomes

Prokaryotes carry clusters of phage defense systems in "defense islands" that have been extensively exploited bioinformatically and experimentally for discovery of immune functions. However, little effort has been dedicated to determining which specific system(s) within defense islands limit lytic phage reproduction in clinical bacterial strains. Here, we employed the CRISPR-based Cascade-Cas3 system to delete defense islands in a Pseudomonas aeruginosa clinical isolate to identify mechanisms of lytic phage antagonism. Deletion of one island in a cystic fibrosis-derived clinical isolate sensitized the strain to phages from the Pbunavirus family, which are commonly used as therapeutics. The causal defense system is a Type IIS restriction endonuclease-like protein (ENDPaCF1), common in Pseudomonads, however it lacks an associated methyltransferase typical Type IIS R-M systems. ENDPaCF1 protects bacteria against phages with hypermodified DNA and is surprisingly agnostic to the specific structure of the modification, which is unlike typical type IV restriction endonucleases. In ENDPaCF1, the endonuclease domain is fused to a catalytically inactive Endonuclease III (iEndoIII), a domain that recognizes non-canonical bases to repair DNA in prokaryotes and eukaryotes. We therefore propose that nucleases containing an iEndoIII domain (END nucleases) can sense diverse DNA hypermodifications. Our findings reveal modularity of the sensing and cleavage domains, as expected of a modification-dependent endonucleases. We further show that some hypermodified phages, including Pbunavirus family members and Wrowclawvirus family (Pa5oct-like) of jumbo phages, encode END nuclease inhibitors that directly bind to the nuclease, likely via the iEndoIII domain. These inhibitors are necessary for Pbunavirus to plaque on clinical isolates and sufficient to enable other hypermodified phages to plaque in the presence of this defense system.

microbiology↗

bioRxiv2024

Ecological Determinants of Altruism in Prokaryote Antivirus Defense

Prokaryote evolution is driven in large part by the incessant arms race with viruses. Genomic investments in antivirus defense can be coarsely classified into two categories, immune systems that abrogate virus reproduction resulting in clearance, and altruistic programmed cell death (PCD) systems. Prokaryotic defense systems are enormously diverse, as revealed by an avalanche of recent discoveries, but the basic ecological determinants of defense strategy remain poorly understood. Through mathematical modeling of defense against lytic virus infection, we identify two principal determinants of optimal defense strategy and, through comparative genomics, we test this model by measuring the genomic investment into immunity vs PCD among diverse bacteria and archaea. First, as viral pressure grows, immunity becomes the preferred defense strategy. Second, as host population size grows, PCD becomes the preferred strategy. We additionally predict that, although optimal strategy typically involves investment in both PCD and immunity, overinvestment in immunity can result in system antagonism, increasing the probability a PCD-competent cell will lyse due to infection. Together these findings indicate that, generally, PCD is preferred at low multiplicity of infection (MOI) and immunity is preferred at high MOI, and that the landscape of prokaryotic antivirus defense is substantially more complex than previously suspected.

microbiology↗

bioRxiv2024

Beyond bacterial paradigms: uncovering the functional significance and first biogenesis machinery of archaeal lipoproteins

Lipoproteins are major constituents of prokaryotic cell surfaces. In bacteria, lipoprotein attachment to membrane lipids is catalyzed by prolipoprotein diacylglyceryl transferase (Lgt). However, no Lgt homologs have been identified in archaea, suggesting the unique archaeal membrane lipids require distinct enzymes for lipoprotein lipidation. Here, we performed in silico predictions for all major archaeal lineages and revealed a high prevalence of lipoproteins across the domain Archaea. Using comparative genomics, we identified the first set of candidates for archaeal lipoprotein biogenesis components (Ali). Genetic and biochemical characterization confirmed two paralogous genes, aliA and aliB, are important for lipoprotein lipidation in the archaeon Haloferax volcanii. Disruption of AliA- and AliB-mediated lipoprotein lipidation results in severe growth defects, decreased motility, and cell-shape alterations, underscoring the importance of lipoproteins in archaeal cell physiology. AliA and AliB also exhibit different enzymatic activities, including potential substrate selectivity, uncovering a new layer of regulation for prokaryotic lipoprotein lipidation.

microbiology↗

bioRxiv2024

Long range segmentation of prokaryotic genomes by gene age and functionality

Bacterial and archaeal genomes encompass numerous operons that typically consist of two to five genes. On larger scales, however, gene order is poorly conserved through the evolution of prokaryotes. Nevertheless, non-random localization of different classes of genes on prokaryotic chromosomes could reflect important functional and evolutionary constraints. We explored the patterns of genomic localization of evolutionarily conserved (ancient) and variable (young) genes across the diversity of bacteria and archaea. Nearly all bacterial and archaeal chromosomes were found to encompass large segments of 100-300 kilobases that were significantly enriched in either ancient or young genes. Similar clustering of genes with lethal knockout phenotype (essential genes) was observed as well. Mathematical modeling of genome evolution suggests that this long-range gene clustering in prokaryotic chromosomes reflects perpetual genome rearrangement driven by a combination of selective and neutral processes rather than evolutionary conservation.

genomics↗

bioRxiv2024

Diversity, Origin and Evolution of the ESCRT Systems

Endosomal Sorting Complexes Required for Transport (ESCRT) play key roles in protein sorting between membrane-bounded compartments of eukaryotic cells. Homologs of many ESCRT components are identifiable in various groups of archaea, especially in Asgardarchaeota, the archaeal phylum that is currently considered to include the closest relatives of eukaryotes, but not in bacteria. We performed a comprehensive search for ESCRT protein homologs in archaea and reconstructed ESCRT evolution using the phylogenetic tree of Vps4 ATPase (ESCRT IV) as a scaffold, using sensitive protein sequence analysis and comparison of structural models to identify previously unknown ESCRT proteins. Several distinct groups of ESCRT systems in archaea outside of Asgard were identified, including proteins structurally similar to ESCRT-I and ESCRT-II, and several other domains involved in protein sorting in eukaryotes, suggesting an early origin of these components. Additionally, distant homologs of CdvA proteins were identified in Thermoproteales which are likely components of the uncharacterized cell division system in these archaea. We propose an evolutionary scenario for the origin of eukaryotic and Asgard ESCRT complexes from ancestral building blocks, namely, the Vps4 ATPase, ESCRT-III components, wH (winged helix-turn-helix fold) and possibly also coiled-coil, and Vps28-like domains. The Last Archaeal Common Ancestor likely encompassed a complex ESCRT system that was involved in protein sorting. Subsequent evolution involved either simplification, as in the TACK superphylum, where ESCRT was co-opted for cell division, or complexification as in Asgardarchaeota. In Asgardarchaeota, the connection between ESCRT and the ubiquitin system that was previously considered a eukaryotic signature was already established. ImportanceAll eukaryotic cells possess complex intracellular membrane organization. ESCRT (Endosomal Sorting Complexes Required for Transport) plays a central role in membrane remodeling which is essential for cellular functionality in eukaryotes. Recently, it has been shown that Asgard archaea, the archaeal phylum that includes the closest known relatives of eukaryotes, encode homologs of many components of the ESCRT systems. We employed protein sequence and structure comparisons to reconstruct the evolution of ESCRT systems in archaea and identified several previously unknown homologs of ESCRT subunits, some of which can be predicted to participate in cell division. The results of this reconstruction indicate that the Last Archaeal Common ancestor already encoded a complex ESCRT system that was involved in protein sorting. In Asgard archaea, ESCRT systems evolved towards greater complexity, and in particular, the connection between ESCRT and the ubiquitin system that was previously considered a eukaryotic signature was established.

evolutionary biology↗

bioRxiv2023

Astonishing diversity and multifaceted biological connections of Type IV restriction-modification systems

A comprehensive census of McrBC systems, among the most common forms of prokaryotic Type IV restriction systems, followed by phylogenetic analysis, reveals their enormous abundance in diverse prokaryotes and a plethora of genomic associations. We focus on a previously uncharacterized branch, which we denote CoCoNuTs (coiled-coil nuclease tandems) for their salient features: the presence of extensive coiled-coil structures and tandem nucleases. The CoCoNuTs alone show extraordinary variety, with 3 distinct types and multiple subtypes. All CoCoNuTs contain domains predicted to interact with translation system components, such as OB-folds resembling the SmpB protein that binds bacterial transfer-messenger RNA (tmRNA), YTH-like domains that might recognize methylated tmRNA, tRNA, or rRNA, and RNA-binding Hsp70 chaperone homologs, along with RNases, such as HEPN domains, all suggesting that the CoCoNuTs target RNA. Many CoCoNuTs might additionally target DNA, via McrC nuclease homologs. Additional restriction systems, such as Type I RM, BREX, and Druantia Type III, are frequently encoded in the same predicted superoperons. In many of these superoperons, CoCoNuTs are likely regulated by cyclic nucleotides, possibly, RNA fragments with cyclic termini, that bind associated CARF (CRISPR-Associated Rossmann Fold) domains. We hypothesize that the CoCoNuTs, together with the ancillary restriction factors, employ an echeloned defense strategy analogous to that of Type III CRISPR-Cas systems, in which an immune response eliminating virus DNA and/or RNA is launched first, but then, if it fails, an abortive infection response leading to PCD/dormancy via host RNA cleavage takes over.

microbiology↗

bioRxiv2023

Parallelized screening of virus accessory genes reveals diverse defense and counter-defense mechanisms

Viruses have been evolving host-modifying factors for billions of years. Genomes of bacterial and archaeal viruses are replete with fast-evolving, uncharacterized accessory genes (AGs), most of which likely antagonize host defenses or other viruses1, 2. Systematic investigation of AGs could uncover a multitude of biological mechanisms involved in virus-host competition, but AG identification in genomic databases remains a challenge. We developed an integrated computational and high-throughput discovery platform to identify AGs in virus genomes and assay their functions in complementary phage infection-dependent and -independent contexts. Our approach showcases how phages interact with the principal layers of antiviral immunity, including cell surface modifications, restriction systems, and abortive infection (Abi) mechanisms, which operate simultaneously in the same host. We discovered multiple Enterobacteriophage AGs associated with counter-defense functions that activate rather than inhibit antiviral immunity in cells, including the surprising finding that anti-restriction AGs elicit programmed cell death (PCD) activity of some restriction-modification (R-M) systems. We propose that counter-defense AGs that trigger PCD create a conundrum for phages whereby keeping the AGs causes PCD but losing them exposes the phage to restriction by bacteria. Strategies employed by viruses to avoid this double jeopardy could be an important factor in virus evolution that remains to be explored.

microbiology↗

bioRxiv2023

Widespread CRISPR repeat-like RNA regulatory elements in CRISPR-Cas systems

CRISPR-cas loci typically contain CRISPR arrays with unique spacers separating direct repeats. Spacers along with portions of adjacent repeats are transcribed and processed into CRISPR(cr) RNAs that target complementary sequences (protospacers) in mobile genetic elements, resulting in cleavage of the target DNA or RNA. Additional, standalone repeats in some CRISPR-cas loci produce distinct cr-like RNAs implicated in regulatory or other functions. We developed a computational pipeline to systematically predict crRNA-like elements by scanning for standalone repeat sequences that are conserved in closely related CRISPR-cas loci. Numerous crRNA-like elements were detected in diverse CRISPR-Cas systems, mostly, of type I, but also subtype V-A. Standalone repeats often form mini-arrays containing two repeat-like sequence separated by a spacer that is partially complementary to promoter regions of cas genes, in particular cas8, or cargo genes located within CRISPR-Cas loci, such as toxins-antitoxins. We show experimentally that a mini-array from a type I-F1 CRISPR-Cas system functions as a regulatory guide. We also identified mini-arrays in bacteriophages that could abrogate CRISPR immunity by inhibiting effector expression. Thus, recruitment of CRISPR effectors for regulatory functions via spacers with partial complementarity to the target is a common feature of diverse CRISPR-Cas systems.

genomics↗

bioRxiv2022

Tail-tape-fused virion and non-virion RNA polymerases of a thermophilic virus with an extremely long tail

Thermus thermophilus bacteriophage P23-45 encodes a giant 5,002-residue tail tape measure protein (TMP)1 that defines the length of its extraordinarily long 800 nm tail2,3. We found that the N-terminal portion of P23-45 TMP is an unusual RNA polymerase (RNAP) homologous to cellular and viral two-barrel RNAPs. The TMP-fused virion RNAP transcribes pre-early phage genes, including a gene that encodes another, non-virion RNAP, that transcribes early and some middle phage genes. We determined the crystal structures of both P23-45 RNAPs. The non-virion RNAP has a crab claw-like architecture similar to previously reported two-barrel RNAPs. The virion RNAP adopts a unique flat structure without a clamp, which likely reflects the requirement for its extrusion through the narrow channel in the phage tail for delivery into the cell. Structure and sequence comparisons of the P23-45 RNAPs with other phage and cellular RNAPs suggest that, despite the extensive functional differences, the two P23-45 RNAPs originate from an ancient gene duplication in an ancestral phage. Our findings demonstrate remarkable adaptability of two-barrel RNAPs that can be attained within a single virus species.

molecular biology↗

bioRxiv2022

A family of novel immune systems targets early infection of nucleus-forming jumbo phages

Jumbo bacteriophages of the [ovbar]KZ-like family are characterized by large genomes (>200 kb) and the remarkable ability to assemble a proteinaceous nucleus-like structure. The nucleus protects the phage genome from canonical DNA-targeting immune systems, such as CRISPR-Cas and restriction-modification. We hypothesized that the failure of common bacterial defenses creates selective pressure for immune systems that target the unique jumbo phage biology. Here, we identify the "jumbo phage killer" (Juk) immune system that is deployed by a clinical isolate of Pseudomonas aeruginosa to resist [ovbar]KZ. Juk immunity rescues the cell by preventing early phage transcription, DNA replication, and nucleus assembly. Phage infection is first sensed by JukA (formerly YaaW), which localizes rapidly to the site of phage infection at the cell pole, triggered by ejected phage factors. The effector protein JukB is recruited by JukA, which is required to enable immunity and the subsequent degradation of the phage DNA. JukA homologs are found in several bacterial phyla and are associated with numerous other putative effectors, many of which provided specific anti-[ovbar]KZ activity when expressed in P. aeruginosa. Together, these data reveal a novel strategy for immunity whereby immune factors are recruited to the site of phage protein and DNA ejection to prevent phage progression and save the cell.

microbiology↗

bioRxiv2022

RNA-triggered protein cleavage and cell death by the RNA-guided type III-E CRISPR-Cas nuclease-protease complex

The type III-E Cas7-11 effector nuclease forms a complex with a CRISPR RNA (crRNA) and the putative caspase-like protease Csx29, catalyzes crRNA-guided target RNA cleavage, and has been used for RNA targeting in eukaryotic cells. Here, we report cryo-electron microscopy structures of the Cas7-11-crRNA-Csx29 complex with and without target RNA, and demonstrate that target RNA binding induces a conformational change in Csx29 and results in the protease activation. Biochemical analysis confirmed that Cas7-11-bound Csx29 cleaves Csx30 in a target RNA-dependent manner. Reconstitution of the system in bacteria uncovered Csx30-dependent cellular toxicity regulated by Csx31, and that Csx29-mediated cleavage produces toxic Csx30 fragments, promoting cell death. We find that Csx30 can bind both Csx31 and the associated sigma factor RpoE, suggesting Csx30 can inhibit RpoE and modulate cellular stress response towards infection. Overall, the RNA-guided nuclease-protease activities of the Cas7-11-Csx29 effector complex facilitate protease-based programmed cell death.

molecular biology↗

bioRxiv2021

tRNA anticodon cleavage by target-activated CRISPR-Cas13a effector

Type VI CRISPR-Cas systems are the only CRISPR variety that cleaves exclusively RNA1,2. In addition to the CRISPR RNA (crRNA)-guided, sequence-specific binding and cleavage of target RNAs, such as phage transcripts, the type VI effector, Cas13, causes collateral RNA cleavage, which induces bacterial cell dormancy, thus protecting the host population from phage spread3,4. We show here that the principal form of collateral RNA degradation elicited by Cas13a protein from Leptotrichia shahii upon target RNA recognition is the cleavage of anticodons of multiple tRNA species, primarily those with anticodons containing uridines. This tRNA cleavage is necessary and sufficient for bacterial dormancy induction by Cas13a. In addition, Cas13a activates the RNases of bacterial toxin-antitoxin modules, thus indirectly causing mRNA and rRNA cleavage, which could provide a back-up defense mechanism. The identified mode of action of Cas13a resembles that of bacterial anticodon nucleases involved in antiphage defense5, which is compatible with the hypothesis that type VI effectors evolved from an abortive infection module6,7 encompassing an anticodon nuclease.

microbiology↗

bioRxiv2020

CRISPRIdentify: Identification of CRISPR arrays using machine learning approach

CRISPR-Cas are adaptive immune systems that degrade foreign genetic elements in archaea and bacteria. In carrying out their immune functions, CRISPR- Cas systems heavily rely on RNA components. These CRISPR (cr) RNAs are repeat-spacer units that are produced by processing of pre-crRNA, the transcript of CRISPR arrays, and guide Cas protein(s) to the cognate invading nucleic acids, enabling their destruction. Several bioinformatics tools have been developed to detect CRISPR arrays based solely on DNA sequences, but all these tools employ the same strategy of looking for repetitive patterns, which might correspond to CRISPR array repeats. The identified patterns are evaluated using a fixed, built-in scoring function, and arrays exceeding a cut-off value are reported. Here, we instead introduce a data-driven approach that uses machine learning to detect and differentiate true CRISPR arrays from false ones based on several features. Our CRISPR detection tool, CRISPRidentify, performs three steps: detection, feature extraction and classification based on manually curated sets of positive and negative examples of CRISPR arrays. The identified CRISPR arrays are then reported to the user accompanied by detailed annotation. We demonstrate that our approach identifies not only previously detected CRISPR arrays, but also CRISPR array candidates not detected by other tools. Compared to other methods, our tool has a drastically reduced false positive rate. In contrast to the existing tools, our approach not only provides the user with the basic statistics on the identified CRISPR arrays but also produces a certainty score as a practical measure of the likelihood that a given genomic region is a CRISPR array.

bioinformatics↗

bioRxiv2020

Expanding diversity of Asgard archaea and the elusive ancestry of eukaryotes

Comparative analysis of 162 (nearly) complete genomes of Asgard archaea, including 75 not reported previously, substantially expands the phylogenetic and metabolic diversity of the Asgard superphylum, with six additional phyla proposed. Phylogenetic analysis does not strongly support origin of eukaryotes from within Asgard, leaning instead towards a three-domain topology, with eukaryotes branching outside archaea. Comprehensive protein domain analysis in the 162 Asgard genomes results in a major expansion of the set of eukaryote signature proteins (ESPs). The Asgard ESPs show variable phyletic distributions and domain architectures, suggestive of dynamic evolution via horizontal gene transfer (HGT), gene loss, gene duplication and domain shuffling. The results appear best compatible with the origin of the conserved core of eukaryote genes from an unknown ancestral lineage deep within or outside the extant archaeal diversity. Such hypothetical ancestors would accumulate components of the mobile archaeal eukaryome via extensive HGT, eventually, giving rise to eukaryote-like cells.

genomics↗

bioRxiv2020

Structure and function of virion RNA polymerase of crAss-like phage

CrAss-like phages are a recently described family-level group of viruses that includes the most abundant virus in the human gut1,2. Genomes of all crAss-like phages encode a large virion-packaged protein2,3 that contains a DFDxD sequence motif, which forms the catalytic site in cellular multisubunit RNA polymerases (RNAPs)4. Using Cellulophaga baltica crAss-like phage phi14:2 as a model system, we show that this protein is a novel DNA-dependent RNAP that is translocated into the host cell along with the phage DNA and transcribes early phage genes. We determined the crystal structure of this 2,180-residue enzyme in a self-inhibited, likely pre-virion-packaged state. This conformation is attained with the help of a Cleft-blocking domain that interacts with the active site motif and occupies the RNA-DNA hybrid binding grove. Structurally, phi14:2 RNAP is most similar to eukaryotic RNAPs involved in RNA interference5,6, although most of phi14:2 RNAP structure (nearly 1,600 residues) maps to a new region of protein folding space. Considering the structural similarity, we propose that eukaryal RNA interference polymerases take their origin in a phage, which parallels the emergence of the mitochondrial transcription apparatus7.

molecular biology↗