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Research Overview of the group of
Molecular Genetics of Differentiation and
Secondary Metabolism of Streptomyces
Prof. Dr. Huarong Tan
Part I. Introduction
This group is focused on the molecular mechanism regulating the spatial and
temporal expression of genes involved in the development and differentiation of
Streptomyces. Also studies on the microbial secondary metabolism, important
biosynthetic pathways including the specific and global regulation of genes, the
ultimate goal is to improve the productivity of the producing-strains and to obtain
novel metabolites.
Group
Leader:
Research Teams:
Ph.D. Professor Huarong Tan
Gang Liu, Ph.D., Associate Professor.
Haihua Yang, Ph.D., Associate Professor.
Yuqing Tian, MSc., Research Associate.
10 Ph. D. Students and 6 MSc. Students.
Part II. Background and Significance
The current researches in this group fall into two major areas:
1. Molecular regulation of differentiation in Streptomyces
The development and differentiation is an important research field in modern
biology. Streptomyces gradually become the most attractive model system, because of
its complex life cycle of morphological differentiation and incomparable ability to
produce a wide variety of secondary metabolites. Streptomyces ansochromogenes, a
nikkomycin producer, was isolated from soil in the northeast of China. This strain has
a typical developmental process from substrate mycelium to spore formation of
Streptomyces species. Several genes related to the differentiation of Streptomyces
ansochromogenes and Streptomyces coelicolor have been cloned, and the function of
these genes have been studied.
Above results suggested that these genes play
important roles in the development and differentiation of Streptomyces.
2. Molecular Genetics of nikkomycin biosynthesis in S. ansochromogenes
The main antibiotics produced by S. ansochromogenes are nikkomycin X and Z.
Nikkomycin is a nucleoside-peptide antibiotic, as a potent competitive inhibitor of
chitin synthetase, it inhibits the biosynthesis of chitin in cell wall due to its structural
resemblance to UDP-N-acetylglucosamine. Nikkomycin inhibiting the growth of
pathogenic fungi, insects and acarids, is non-toxic to mammals, plants and bees, and
is easily degraded in nature. Nikkomycin biosynthesis has been investigated
extensively, but the biosynthetic pathway remains unknown. In order to elucidate
the pathway and to improve nikkomycin productivity, the gene cluster of nikkomycin
biosynthesis has been cloned and sequenced. The function of most genes has been
studied, suggesting that these genes are essential for nikkomycin biosynthesis in S.
ansochromogenes.
Part III. Major Achievements
samR, a novel Streptomyces gene, can accelerate mycelium formation of S.
ansochromogenes when present on a multicopy plasmid, whereas samR disruption
failed to form aerial and spores (Tan et al., Arch. Microbiol., 2002). WhiI, a regulator
required for spore septation in the development and differentiation of Streptomyces, is
structurally similar to response regulators of bacterial two-component systems, but
lacks some conserved features of typical phosphorylation pockets. whiI disruption
affected the expression of 45 genes, 23 of them were upregulated and 22 of them were
downregulated (paper in preparation). sanG encodes a transcriptional activator
important
for
secondary
metabolism
and
development
in
Streptomyces
ansochromogenes ( Mol. Microbiol., 2005).
The nikkomycin biosynthetic gene cluster has been cloned previously from
Streptomyces ansochromogenes. The cluster contains 26 complete ORFs including
sanJ, sanO, sanJ, sanU and sanV, which are well-studied. Gene disruption and genetic
complementation revealed that these genes were involved in nikkomycin biosynthesis.
Recombinant strains were constructed by increasing an extra copy of sanU and sanV
in Streptomyces ansochromogenes, by which the nikkomycin production was about 2
fold higher than that of wild-type strain. The sanJ gene was inactivated by the
insertion of kanamycin resistance gene and the resulting disruption mutants failed to
produce nikkomycins. Moreover, the nikkomycin production was recovered by
cis-complementation with a single copy of sanJ. The result indicated that sanJ
encoded an ATP-dependent picolinate-CoA ligase essential for nikkomycin
biosynthesis. A pathway-specific transcriptional regulatory gene, sanG was cloned
and sequenced from Streptomyces ansochromogenes. Disruption of sanG abolished
nikkomycin biosynthesis. This phenotype was complemented by a single copy of
sanG which was integrated into the chromosome. Like most pathway-specific
transcriptional regulatory gene, the introduction of multiple copies of sanG resulted in
increased nikkomycin production. The result suggested that sanG is a positive
regulatory gene for nikkomycin biosynthesis (Mol Microbiol., 2005).
About 30 original research papers were published in recent 4 years, 16 of them
were published in the international journals. Two patents were filed and other two
patents were granted by the National Patent Bureau of China.
Publications in International Journals (2002-2005):
1．Tan Huarong*, Tian Yuqing, Yang Haihua et al..2002. A novel Streptomyces gene, samR , with
different effects on differentiation of Streptomyces ansochromogenes and Streptomyces
coelicolor . Archives of Microbiology , 177 (3): 274-278.
2. Bao Q, Tian Y., Li W, Xu Z, Hu S, Dong W, Xue Y, Xu Y, Lai X, Huang L, Dong X, Ma Y,
Ling L, Tan H*, Chen R, Wang J, Yu J, Yang H. 2002. A complete sequence of the T.
tengcongensis genome. Genome Res . 12(5); 689-700.
3. Zeng Hongmei, Tan Huarong*, Li Jilun. 2002. Cloning and function of sanQ: A gene involved
in nikkomycin biosynthesis of Streptomyces ansochromogenes . Current Microbiol ., 45(3):
175-179.
4. Wei Wenzhong, Xiang Hua, Tan Huarong*. 2002. Two tandem promoters to increase gene
expression in Lactococcus lactis. Biotechnol. Lett., 24: 1669-1672.
6. Zhang Jihui, Ma Wenbo, Tan Huarong* . 2002. Cloning, expression and characterization of a
gene encoding nitroalkane-oxidizing enzyme from Streptomyces ansochromogenes. Eur. J.
Biochem. , 269 (24): 6302-6307.
2002，42（4）
：502-505。
7. Xu Jianyong, Liu Gang, Tan Huarong* . 2003. sanC —a novel gene involved in nikkomycin
biosynthesis in Streptomyces ansochromogenes . Letters in Applied Microbiology , 36:
234-238.
8. Xiang Hua, Wei Wenzhong, Tan Huarong* . 2003. Food-grade expression of human glutathion
S-transferase and Cu/Zn superoxide dismutase in Lactococcus lactis . Biomolecular
Engineering , 20: 107-112.
9. Li Wenli and Tan Huarong* . 2003. Structure and function of sanV : a gene involved in
nikkomycin biosynthetic pathway of Streptomyces ansochromogenes . Current Microbiolog,
46(6) : 403-407.
10. He Xiuping, Zhang Borun*, Tan Huarong* . 2003. Overexpression of a sterol C-24(28)
reductase increases ergosterol production in Saccharomyces cerevisiae . Biotech Lett ., 25
(10): 773-778.
11. Wang Guojun, Nie Liping, Tan Huarong* . 2003. Cloning and characterization of sanO , a
gene involved in nikkomycin biosynthesis in Streptomyces ansochromogenes . Lett. Appl.
Microbiol., 36: 452-457.
12. Li Wenli, Liu Gang, Tan Huarong* . 2003. Disruption of sabR affects nikkomycin
biosynthesis and morphogenesis in Streptomyces ansochromogenes . Biotechnol Lett. 25：
1491-1497.
13. Wang Guojun and Tan Huarong* . 2004. Enhanced production of nikkomycin X by
over-expression
of
SanO,
a
non-ribosomal
peptide
synthetase
in
Streptomyces
ansochromogenes . Biotechnol. Lett., 26(3): 229-233.
14. Li Yirong, Zeng Hongmei and Tan Huarong* . 2004. Cloning, Function and expression of
sansS : A gene essential for nikkomycin biosynthesis of Streptomyces ansochromogenes .
Current Microbiology, 49: 128-132 .
15. Liu Gang, Tian Yuqing, Yang Haihua, Tan Huarong*. 2005. A pathway-specific
transcriptional
regulatory
gene
for
nikkomycin
biosynthesis
in
Streptomyces
ansochromogenes that also influences colony development. Molecular Microbiology, 55 (6):
1855-1866.
16. Li Yirong, Ling Hongbo, Li Wenli, Tan Huarong*. 2005. Improvement of nikkomycin
production by enhanced copy of sanU and sanV in Streptomyces ansochromogenes and
characterization of a novel glutamate mutase encoded by sanU and sanV. Metabolic
Engineering. 7: 165-173.
Patents:
1. Tan Huarong and Liu Gang. 2004. Regulatory gene and engineered strain of nikkomycin
biosynthesis. Filed number: 2004100584112.
2. Tan Huarong and Li Yirong. 2004. Engineered strain and its application of X compenet of
nikkomycin. Filed number: 0313068 61.
3. Tan Huarong, Zhang Jihui and Ma Wenbo. 2004. Gene encoding nitroalkane-oxidizing
enzyme and its application. Granted number: ZL01142017.0
4. Tan Huarong, Zeng Hongmei. 2005. Engineered strain and its application of Z compenet of
nikkomycin. Granted number: ZL01142016.2.
Part IV. Future Research Plan
1. The biosynthetic pathway of nikkomycin will be further studied and to reveal the
molecular machanism of genes involved in the pathway, using nikkomycin as a
model system to clarify the biosynthetic properties of nucleoside-peptide
antibiotics.
2. Some important genes related to the development and differentiation of
Streptomyces will be further studied, which include whiI, sanG and scrX.
3.
Interaction between genes concerning differentiation and antibiotic biosynthesis.
4. Heterologous expression of the nikkomycin gene cluster, modification of
biosynthetic pathway and combinatorial biosynthesis.