## 3 Mycobacteriumophages--General Characteristics and Overview
& \multicolumn{2}{c}{widely used in mycobacterial genetics} & \multirow{2}{*}{1951/[PERSON]} \\  & & & long flexible tail & & & & **as a tool for** & E. \\  & & & long flexible tail & & & & **[32]** \\  & & & long flexible tail & & & & **[Reference]** \\ \hline \multirow{2}{*}{_Poloviralae_} & \multirow{2}{*}{dsDNA, linear} & \multirow{2}{*}{\(\Phi\)29} & Complex structure, short tail & \multirow{2}{*}{_Bacillus_ sp.} & \multicolumn{2}{c}{widely used in molecular biology for its high-fidelity DNA polymerase and DNA replication studies} & \multirow{2}{*}{1965/[PERSON]} \\  & & & & & & **[Reference]** \\ \hline \multirow{2}{*}{_Tectiviralae_} & \multirow{2}{*}{dsDNA, linear} & \multirow{2}{*}{PRD1} & Isometric structure, lipoprotein vesicle & \multirow{2}{*}{_Escherichia coli_} & \multirow{2}{*}{_Escherichia coli_} & \multirow{2}{*}{1984/[PERSON]} \\  & & & & & & **[34]** \\  & & & & & & **[35]** \\  & & & & & & **[36]** \\  & & & & & & **[37]** \\  &research but are also being explored as diagnostic tools and therapeutic agents, particularly in cases of drug-resistant _Mycobacterium_ infections. Most mycobacteriophages belong to the _Siphooviridae_ family, within which there is a strong variation in the length of the non-contractile tail and the symmetry of the phage head. The genomes of mycobacteriophages from this family range from 22 to 140 kbp. Mycobacteriophages from the _Myoviidae_ family have shorter, contractile tails, which allow them to penetrate the bacterial membrane and inject their genetic material into the host cell. The genomes of these phages range from 30 to 500 kbp [43; 53]. The first complete mycobacteriophage genome was sequenced in 1993. It belonged to phage L5, which is closely related to phage L1, a virus that infects both fast- and slow-growing species of mycobacteria. The next fully sequenced phage was mycobacteriophage D29, which shared sequence similarity with phage L5, particularly in the genes coding for structural elements of the virion [54]. The third sequenced genome was that of phage TM4, isolated from _M. avium_[43]. However, it was soon found that this phage could infect not only _M. avium_ but also _M. smegmatis_ and _M. tuberculosis_[55]. Comparative analysis of the TM4 genome showed significant differences from the genomes of mycobacteriophages L5 and D29. By 2010, a total of 60 complete mycobacteriophage genomes had been deposited in GenBank, originating from various geographical regions and environments. However, it is worth noting that more than half of these were isolated from the western Pennsylvania  
Figure 1: Overview of mycobacteriophage characteristics and classification. All currently known mycobacteriaj belongs to the order _Caudovirales_, specifically to two of its three families: _Siphoviridae_ and _Myoviidae_. They possess double-stranded DNA (dsDNA), tails, and isometric heads, although some—such as Corndog, Che9c, and Brujita—have prolate heads. Genome sizes vary considerably, from approximately 40 kilobase pairs (kbp) to 150 kbp. Mycobacteriumjophages are classified into clusters based on an arbitrary criterion: genomes sharing more than 50% nucleotide identity across their entire length are grouped together. As of 2018, 28 clusters and 5 singleton phages have been identified, along with several subclusters. In 2020–2021, seven new mycobacteriajophages with _Siphooviridae_-like morphology were isolated from soil samples in Texas, USA, and assigned to the following clusters based on genomic analysis: Duplo, Gilbert, and MaCh (A); Dynamo (P); Nikao (K); Phloss (N); and Skinny (M). Based on Refs. [43; 44; 49; 50; 51; 52]. region of the USA. The limited number of phage isolations from other countries does not appear to be due to their absence in the environment, but rather the costly and time-consuming process of their isolation [43]. Despite the isolation of approximately 2400 different mycobacteriophage types from numerous clinical and environmental mycobacterial species, by 2012, the genomes of 221 mycobacteriophages had been fully sequenced.