1
|
Sood U, Müller M, Lan T, Garg G, Singhvi N, Hira P, Singh P, Nigam A, Verma M, Lata P, Kaur H, Kumar A, Rawat CD, Lal S, Aldrich C, Bechthold A, Lal R. Amycolatopsis mediterranei: A Sixty-Year Journey from Strain Isolation to Unlocking Its Potential of Rifamycin Analogue Production by Combinatorial Biosynthesis. JOURNAL OF NATURAL PRODUCTS 2024; 87:424-438. [PMID: 38289177 DOI: 10.1021/acs.jnatprod.3c00686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/24/2024]
Abstract
Ever since the isolation of Amycolatopsis mediterranei in 1957, this strain has been the focus of research worldwide. In the last 60 years or more, our understanding of the taxonomy, development of cloning vectors and conjugation system, physiology, genetics, genomics, and biosynthetic pathway of rifamycin B production in A. mediterranei has substantially increased. In particular, the development of cloning vectors, transformation system, characterization of the rifamycin biosynthetic gene cluster, and the regulation of rifamycin B production by the pioneering work of Heinz Floss have made the rifamycin polyketide biosynthetic gene cluster (PKS) an attractive target for extensive genetic manipulations to produce rifamycin B analogues which could be effective against multi-drug-resistant tuberculosis. Additionally, a better understanding of the regulation of rifamycin B production and the application of newer genomics tools, including CRISPR-assisted genome editing systems, might prove useful to overcome the limitations associated with low production of rifamycin analogues.
Collapse
Affiliation(s)
- Utkarsh Sood
- Department of Zoology, Kirori Mal College, University of Delhi, Delhi-110007, India
| | - Moritz Müller
- Institute of Pharmaceutical Biology and Biotechnology, Albert-Ludwigs-Universität, Stefan-Meier-Straße 19, 79104, Freiburg, Germany
| | - Tian Lan
- Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Gauri Garg
- Department of Zoology, Kirori Mal College, University of Delhi, Delhi-110007, India
| | - Nirjara Singhvi
- School of Allied Sciences, Dev Bhoomi Uttarakhand University, Dehradun, Uttarakhand 248007, India
| | - Princy Hira
- Department of Zoology, Maitreyi College, University of Delhi, Delhi-110003, India
| | - Priya Singh
- Department of Zoology, Maitreyi College, University of Delhi, Delhi-110003, India
| | - Aeshna Nigam
- Department of Zoology, Shivaji College, University of Delhi, Delhi-110027, India
| | - Mansi Verma
- Department of Zoology, Hansraj College, University of Delhi, Delhi-110007, India
| | - Pushp Lata
- Department of Zoology, University of Delhi, Delhi-110007, India
| | - Hardeep Kaur
- Department of Zoology, Ramjas College, University of Delhi, Delhi-110007, India
| | - Abhilash Kumar
- Department of Zoology, Ramjas College, University of Delhi, Delhi-110007, India
| | - Charu Dogra Rawat
- Department of Zoology, Ramjas College, University of Delhi, Delhi-110007, India
| | - Sukanya Lal
- PhiXGen Private Limited, Gurugram, Haryana-122001, India
| | - Courtney Aldrich
- Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Andreas Bechthold
- Institute of Pharmaceutical Biology and Biotechnology, Albert-Ludwigs-Universität, Stefan-Meier-Straße 19, 79104, Freiburg, Germany
| | - Rup Lal
- PhiXGen Private Limited, Gurugram, Haryana-122001, India
- Acharya Narendra Dev College, University of Delhi, Delhi-110019, India
| |
Collapse
|
2
|
Looking Back to Amycolatopsis: History of the Antibiotic Discovery and Future Prospects. Antibiotics (Basel) 2021; 10:antibiotics10101254. [PMID: 34680834 PMCID: PMC8532670 DOI: 10.3390/antibiotics10101254] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Revised: 10/07/2021] [Accepted: 10/12/2021] [Indexed: 11/17/2022] Open
Abstract
The emergence of antibiotic-resistant pathogenic bacteria in recent decades leads us to an urgent need for the development of new antibacterial agents. The species of the genus Amycolatopsis are known as producers of secondary metabolites that are used in medicine and agriculture. The complete genome sequences of the Amycolatopsis demonstrate a wide variety of biosynthetic gene clusters, which highlights the potential ability of actinomycetes of this genus to produce new antibiotics. In this review, we summarize information about antibiotics produced by Amycolatopsis species. This knowledge demonstrates the prospects for further study of this genus as an enormous source of antibiotics.
Collapse
|
3
|
Kumari R, Singh P, Lal R. Genetics and Genomics of the Genus Amycolatopsis. Indian J Microbiol 2016; 56:233-46. [PMID: 27407288 PMCID: PMC4920768 DOI: 10.1007/s12088-016-0590-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Accepted: 04/23/2016] [Indexed: 02/06/2023] Open
Abstract
Actinobacteria are gram-positive filamentous bacteria which contains some of the most deadly human pathogens (Mycobacterium tuberculosis, M. leprae, Corynebacterium diphtheriae, Nocardia farcinica), plant pathogens (Streptomyces scabies, Leifsonia xyli) along with organisms that produces antibiotic (Streptomycetes, Amycolatopsis, Salinospora). Interestingly, these bacteria are equipped with an extraordinary capability of producing antibiotics and other metabolites which have medicinal properties. With the advent of inexpensive genome sequencing techniques and their clinical importance, many genomes of Actinobacteria have been successfully sequenced. These days, with the constant increasing number of drug-resistant bacteria, the urgent need for discovering new antibiotics has emerged as a major scientific challenge. And, unfortunately the traditional method of screening bacterial strains for the production of antibiotics has decreased leading to a paradigm shift in the planning and execution of discovery of novel biosynthetic gene clusters via genome mining process. The entire focus has shifted to the evaluation of genetic capacity of organisms for metabolite production and activation of cryptic gene clusters. This has been made possible only due to the availability of genome sequencing and has been augmented by genomic studies and new biotechnological approaches. Through this article, we present the analysis of the genomes of species belonging to the genus Amycolatopsis, sequenced till date with a focus on completely sequenced genomes and their application for further studies.
Collapse
Affiliation(s)
- Rashmi Kumari
- Molecular Biology Laboratory, Department of Zoology, University of Delhi, Delhi, 110007 India
| | - Priya Singh
- Molecular Biology Laboratory, Department of Zoology, University of Delhi, Delhi, 110007 India
| | - Rup Lal
- Molecular Biology Laboratory, Department of Zoology, University of Delhi, Delhi, 110007 India
| |
Collapse
|
4
|
Nigam A, Almabruk KH, Saxena A, Yang J, Mukherjee U, Kaur H, Kohli P, Kumari R, Singh P, Zakharov LN, Singh Y, Mahmud T, Lal R. Modification of rifamycin polyketide backbone leads to improved drug activity against rifampicin-resistant Mycobacterium tuberculosis. J Biol Chem 2015; 289:21142-52. [PMID: 24923585 DOI: 10.1074/jbc.m114.572636] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rifamycin B, a product of Amycolatopsis mediterranei S699, is the precursor of clinically used antibiotics that are effective against tuberculosis, leprosy, and AIDS-related mycobacterial infections. However, prolonged usage of these antibiotics has resulted in the emergence of rifamycin-resistant strains of Mycobacterium tuberculosis. As part of our effort to generate better analogs of rifamycin, we substituted the acyltransferase domain of module 6 of rifamycin polyketide synthase with that of module 2 of rapamycin polyketide synthase. The resulting mutants (rifAT6::rapAT2) of A. mediterranei S699 produced new rifamycin analogs, 24-desmethylrifamycin B and 24-desmethylrifamycin SV, which contained modification in the polyketide backbone. 24-Desmethylrifamycin B was then converted to 24-desmethylrifamycin S, whose structure was confirmed by MS, NMR, and X-ray crystallography. Subsequently, 24-desmethylrifamycin S was converted to 24-desmethylrifampicin, which showed excellent antibacterial activity against several rifampicin-resistant M. tuberculosis strains.
Collapse
|
5
|
Peano C, Damiano F, Forcato M, Pietrelli A, Palumbo C, Corti G, Siculella L, Fuligni F, Tagliazucchi GM, De Benedetto GE, Bicciato S, De Bellis G, Alifano P. Comparative genomics revealed key molecular targets to rapidly convert a reference rifamycin-producing bacterial strain into an overproducer by genetic engineering. Metab Eng 2014; 26:1-16. [DOI: 10.1016/j.ymben.2014.08.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 08/08/2014] [Accepted: 08/10/2014] [Indexed: 10/24/2022]
|
6
|
Draft Genome Sequence of Amycolatopsis mediterranei DSM 40773, a Tangible Antibiotic Producer. GENOME ANNOUNCEMENTS 2014; 2:2/4/e00752-14. [PMID: 25081263 PMCID: PMC4118066 DOI: 10.1128/genomea.00752-14] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Amycolatopsis mediterranei DSM 40773 has been of special interest as successors of this strain are in use for the commercial production of rifamycin B. Here we present the draft genome sequence (~10 Mb) of this strain, which contains 108 contigs, 9,198 genes, and has a G+C content of 71.3%.
Collapse
|
7
|
Complete genome sequence of Amycolatopsis mediterranei S699 based on de novo assembly via a combinatorial sequencing strategy. J Bacteriol 2012; 194:5699-700. [PMID: 23012281 DOI: 10.1128/jb.01295-12] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The genome of Amycolatopsis mediterranei S699 was resequenced and assembled de novo. By comparing the sequences of S699 previously released and that of A. mediterranei U32, about 10 kb of major indels was found to differ between the two S699 genomes, and the differences are likely attributable to their different assembly strategies.
Collapse
|
8
|
Whole genome sequence of the rifamycin B-producing strain Amycolatopsis mediterranei S699. J Bacteriol 2011; 193:5562-3. [PMID: 21914879 DOI: 10.1128/jb.05819-11] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Amycolatopsis mediterranei S699 is an actinomycete that produces an important antibiotic, rifamycin B. Semisynthetic derivatives of rifamycin B are used for the treatment of tuberculosis, leprosy, and AIDS-related mycobacterial infections. Here, we report the complete genome sequence (10.2 Mb) of A. mediterranei S699, with 9,575 predicted coding sequences.
Collapse
|
9
|
El-Bondkly AM, Abd-Alla HI, Shaaban M, Shaaban KA. The Electrospray Ionization - Mass Spectra of Erythromycin A Obtained from a Marine Streptomyces sp. Mutant. Indian J Pharm Sci 2011; 70:310-9. [PMID: 20046738 PMCID: PMC2792501 DOI: 10.4103/0250-474x.42979] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2007] [Revised: 02/12/2008] [Accepted: 05/25/2008] [Indexed: 11/12/2022] Open
Abstract
In our ongoing search for production improvements of bioactive secondary metabolites from marine Streptomyces through the induction of mutations using UV light, out of 145 isolates, mutant 10/14 was able to produce potent antibacterial metabolites other than the parent strain as established by chromatographic analysis. Up-scaling fermentation of mutant 10/14, followed by working up and isolation delivered five metabolites, phenazine, 1-acetyl-β -carboline, perlolyrin and erythromycin A, along with an oily substance. The latter two compounds were responsible for the antibacterial activity of the strain. In this article, we discuss with the mutation of the marine Streptomyces sp. AH2, bioactivity evaluation, fermentation and isolation of the microbial metabolites. Moreover, we study to first time in detail the 1D and 2D NMR and ESI MS data including ESI MS2 and MS3 patterns combined with HRESI MS of erythromycin A.
Collapse
|
10
|
Zhao W, Zhong Y, Yuan H, Wang J, Zheng H, Wang Y, Cen X, Xu F, Bai J, Han X, Lu G, Zhu Y, Shao Z, Yan H, Li C, Peng N, Zhang Z, Zhang Y, Lin W, Fan Y, Qin Z, Hu Y, Zhu B, Wang S, Ding X, Zhao GP. Complete genome sequence of the rifamycin SV-producing Amycolatopsis mediterranei U32 revealed its genetic characteristics in phylogeny and metabolism. Cell Res 2010; 20:1096-108. [DOI: 10.1038/cr.2010.87] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
|
11
|
Bapat PM, Das D, Sohoni SV, Wangikar PP. Hierarchical amino acid utilization and its influence on fermentation dynamics: rifamycin B fermentation using Amycolatopsis mediterranei S699, a case study. Microb Cell Fact 2006; 5:32. [PMID: 17081297 PMCID: PMC1665455 DOI: 10.1186/1475-2859-5-32] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2006] [Accepted: 11/02/2006] [Indexed: 01/08/2023] Open
Abstract
Background Industrial fermentation typically uses complex nitrogen substrates which consist of mixture of amino acids. The uptake of amino acids is known to be mediated by several amino acid transporters with certain preferences. However, models to predict this preferential uptake are not available. We present the stoichiometry for the utilization of amino acids as a sole carbon and nitrogen substrate or along with glucose as an additional carbon source. In the former case, the excess nitrogen provided by the amino acids is excreted by the organism in the form of ammonia. We have developed a cybernetic model to predict the sequence and kinetics of uptake of amino acids. The model is based on the assumption that the growth on a specific substrate is dependent on key enzyme(s) responsible for the uptake and assimilation of the substrates. These enzymes may be regulated by mechanisms of nitrogen catabolite repression. The model hypothesizes that the organism is an optimal strategist and invests resources for the uptake of a substrate that are proportional to the returns. Results Stoichiometric coefficients and kinetic parameters of the model were estimated experimentally for Amycolatopsis mediterranei S699, a rifamycin B overproducer. The model was then used to predict the uptake kinetics in a medium containing cas amino acids. In contrast to the other amino acids, the uptake of proline was not affected by the carbon or nitrogen catabolite repression in this strain. The model accurately predicted simultaneous uptake of amino acids at low cas concentrations and sequential uptake at high cas concentrations. The simulated profile of the key enzymes implies the presence of specific transporters for small groups of amino acids. Conclusion The work demonstrates utility of the cybernetic model in predicting the sequence and kinetics of amino acid uptake in a case study involving Amycolatopsis mediterranei, an industrially important organism. This work also throws some light on amino acid transporters and their regulation in A. mediterranei .Further, cybernetic model based experimental strategy unravels formation and utilization of ammonia as well as its inhibitory role during amino acid uptake. Our results have implications for model based optimization and monitoring of other industrial fermentation processes involving complex nitrogen substrate.
Collapse
Affiliation(s)
- Prashant M Bapat
- Department of Chemical Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai 400 076, India
- Center for Mikrobiel Bioteknologi, BioCentrum-DTU, Danmarks Tekniske Universitet, Bygning 223, DK-2800 Kgs. Lyngby, Denmark
| | - Debasish Das
- Department of Chemical Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai 400 076, India
| | - Sujata V Sohoni
- Department of Chemical Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai 400 076, India
| | - Pramod P Wangikar
- Department of Chemical Engineering, Indian Institute of Technology, Bombay, Powai, Mumbai 400 076, India
| |
Collapse
|
12
|
Kaur H, Cortes J, Leadlay P, Lal R. Cloning and partial characterization of the putative rifamycin biosynthetic gene cluster from the actinomycete Amycolatopsis mediterranei DSM 46095. Microbiol Res 2002; 156:239-46. [PMID: 11716212 DOI: 10.1078/0944-5013-00108] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The actinomycete Amycolatopsis mediterranei produces the commercially and medically important polyketide antibiotic rifamycin, which is widely used against mycobacterial infections. The rifamycin biosynthetic (rif) gene cluster has been isolated, cloned and characterized from A. mediterranei S699 and A. mediterranei LBGA 3136. However, there are several other strains of A. mediterranei which also produce rifamycins. In order to detect the variability in the rif gene cluster among these strains, several strains were screened by PCR amplification using oligonucleotide primers based on the published DNA sequence of the rif gene cluster and by using dEBS II (second component of deoxy-erythronolide biosynthase gene) as a gene probe. Out of eight strains of A. mediterranei selected for the study, seven of them showed the expected amplification of the DNA fragments whereas the amplified DNA pattern was different in strain A. mediterranei DSM 46095. This strain also showed striking differences in the banding pattern obtained after hybridization of its genomic DNA against the dEBS II probe. Initial cloning and characterization of the 4-kb DNA fragment from the strain DSM 46095, representing a part of the putative rifamycin biosynthetic cluster, revealed nearly 10% and 8% differences in the DNA and amino acid sequence, respectively, as compared to that of A. mediterranei S699 and A. mediterranei LBGA 3136. The entire rif gene cluster was later cloned on two cosmids from A. mediterranei DSM 46095. Based on the partial sequence analysis of the cluster and sequence comparison with the published sequence, it was deduced that among eight strains of A. mediterranei, only A. mediterranei DSM 46095 carries a novel rifamycin biosynthetic gene cluster.
Collapse
|
13
|
Murali Krishna PS, Venkateswarlu G, Venkateswar Rao L. Effect of uracil on rifamycin SV production by Amycolatopsis mediterranei MV35R. Lett Appl Microbiol 2000; 31:73-6. [PMID: 10886619 DOI: 10.1046/j.1472-765x.2000.00769.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The effect of different organic nitrogen compounds on the production of rifamycin SV by Amycolatopsis mediterranei MV35R and their optimum concentrations have been described. Results obtained indicate that rifamycin SV production increased from 4020 mg l-1 to 4575 mg l-1 when organic nitrogen compound uracil was added at 0.2% (w/v) concentration to the fermentation medium by A. mediterranei MV35R. The rifamycin SV yield was enhanced by 505 mg l-1 using uracil (2 g l-1) when compared with barbital.
Collapse
|
14
|
Lal R, Kumari R, Kaur H, Khanna R, Dhingra N, Tuteja D. Regulation and manipulation of the gene clusters encoding type-I PKSs. Trends Biotechnol 2000; 18:264-74. [PMID: 10802562 DOI: 10.1016/s0167-7799(00)01443-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Modular polyketide synthases are large, multifunctional enzyme complexes that are involved in the biosynthesis of important polyketides. Recent studies have revolutionized our understanding of the linear organization of polyketide-synthase-gene clusters. They have provided crucial information on the initiation, elongation and termination of polyketide chains, and thus a rational basis for the generation of novel compounds. Combinatorial libraries have helped this field to move from a random approach to a more empirical phase. The large number of diverse analogs of antibiotics that are presently produced demonstrate the enormous potential of combinatorial biosynthesis.
Collapse
Affiliation(s)
- R Lal
- Molecular Biology Laboratory, Department of Zoology, University of Delhi, Delhi 110007, India.
| | | | | | | | | | | |
Collapse
|
15
|
Khanna M, Dua M, Lal R. Selection of suitable marker genes for the development of cloning vectors and electroporation in different strains of Amycolatopsis mediterranei. Microbiol Res 1998; 153:205-11. [PMID: 9880927 DOI: 10.1016/s0944-5013(98)80002-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
To select suitable genetic markers for optimizing electroporation efficiency in Amycolatopsis mediterranei, thiostrepton (tsr), erythromycin (ermE) and apramycin (am) resistance genes were used. Although tsr could not be suitably expressed in A. mediterranei, the cloning of ermE in pRL1 or its derivative (containing am) resulted in the development of cloning vectors pRLM20, pRLM30 and pRL90. In contrast to tsr and km (kanamycin resistance gene), ermE and am were suitably expressed in A. mediterranei strains and no spontaneous mutants were observed among transformants. Under optimum conditions, maximum electroporation efficiency of 1.2 x 10(4) transformants/micrograms DNA was achieved for A. mediterranei DSM 40,773. These plasmids could also be effectively transferred in other strains of A. mediterranei including F1/24 and T-195. With the cloning of ermE and am and their expression in different strains of Amycolatopsis, we have overcome the problem of the choice of suitable selectable markers for A. mediterranei and related species.
Collapse
Affiliation(s)
- M Khanna
- Department of Zoology, University of Delhi, India.
| | | | | |
Collapse
|
16
|
Lal R, Khanna R, Kaur H, Khanna M, Dhingra N, Lal S, Gartemann KH, Eichenlaub R, Ghosh PK. Engineering antibiotic producers to overcome the limitations of classical strain improvement programs. Crit Rev Microbiol 1996; 22:201-55. [PMID: 8989512 DOI: 10.3109/10408419609105481] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Improvement of the antibiotic yield of industrial strains is invariably the main target of industry-oriented research. The approaches used in the past were rational selection, extensive mutagenesis, and biochemical screening. These approaches have their limitations, which are likely to be overcome by the judicious application of recombinant DNA techniques. Efficient cloning vectors and transformation systems have now become available even for antibiotic producers that were previously difficult to manipulate genetically. The genes responsible for antibiotic biosynthesis can now be easily isolated and manipulated. In the first half of this review article, the limitations of classical strain improvement programs and the development of recombinant DNA techniques for cloning and analyzing genes responsible for antibiotic biosynthesis are discussed. The second half of this article addresses some of the major achievements, including the development of genetically engineered microbes, especially with reference to beta-lactams, anthracyclines, and rifamycins.
Collapse
Affiliation(s)
- R Lal
- Department of Zoology, University of Delhi, India
| | | | | | | | | | | | | | | | | |
Collapse
|