Benha University
Faculty of Science
Botany Department
‫سهام محمد شاش‬.‫د‬
3ed year Students
Botany& Chemistry
Actinomycetes
Time: H
Exam: June 2011
Answer the following questions:
---------------------------------------1- Discuss the main characters about three of the following genera:
a) Genus: Streptomyces
b) Genus: Frankia
c) Genus: Thermomonospora
d) Genus: Agromycess
2- Write short notes about the following:
a) production of antibiotics by Actinomycetes.
b) relation of Actinomycets to Bacteria.
3- Complete:
a) Factors influencing Actinomycetes in soil are:
1----------- 2--------- 3------ 4------ 5------- 6 ------- 7------b) Actinomycets morphology depends upon:
1------------2---------3------4------------5---------6-------c) Cultural characteristics of Actinomycets depends upon:
1----------------- 2------------- 3------------- 4-----------d) The criteria used for the description and classification of
Actinomycets are:
1-------------- 2-------------- 3----------- 4-------- 5-----------____________________________________________________________
Good luck
Benha University
Faculty of Science
Botany Department
‫سهام محمد شاش‬.‫د‬
3ed year Students
Time: H
Botany& Chemistry
Exam: June 2011
Actinomycetes
The answers
1- The main characters of :
a) Genus: Streptomyces
================= Vegetative mycelium produce an extensively branched
mycelium that rarely fragments.
The aerial mycelium at maturity forms chains of spores.
A few species bear short chains of spores on the substrate mycelium.
Sclerotia, pycnidial sporangia and synnemata like structures be formed by some
speces.
Spores are non motile.
The organisms produce a wide variety of pigments responsible for the color of the
vegetative and aerial mycelia.
Many strains produce one or more antibiotics.
Aerobes, gram-positive, catalase positive, degrade gelatin, starch and L-tyrosine.
Temperature optimum 25-35, some species grow at temperature within the
psychrophilic and thermophilic range.
b) Genus: Frankia
============== Symbiotic actinomycetes which lived in root nodules of
non-leguminous plants.
The organism was obligate symbiotic capable of fixing atmospheric nitrogen in
root nodules.
The organisms grew well under microaerophilic conditions but not anaerobic.
They form branched septated mycelium and sporogenous bodies with transverse
and longitudinal septation.
Large number of ovoid or polyhedral spores are formed in the sporangia.
c) Genus: Thermomonospora:
===================== produce single, heat sensitive, non-motile
aleuriospores on aerial mycelium.
On agar media, a branched, non-fragment vegetative mycelium forms leathery
colonies usually covered with aerial mycelium.
Spores may be sessile or may often formed at the tips of simple un branched or
branched sporophores.
In many strains repeated sporophore branching leads to the formation of spore
clusters.
Gram-positive. All strains can grow in the temperature 40-48oC.
It can be isolated from soil but are more common in manures, composts and
overheated fodders.
d) Genus: Agromycess
================ Gram-positive, asporogenous, non-motile, catalase
negative. The genus forms a mycelium that fragment into coccoid and branched
rod-like elements. It is microaerophilic to anaerobic, it grows poorly, If at all,
under strictly anaerobic conditions. It is sensitive to lysozyme and has an oxidative
metabolism.
Chemical composition
The wall peptidoglycan contains analine, glycine, glutamic acid, and 2,4diaminobutyric (DAP) acid. The wall sugar composition varies, some strains
contain glucose, mannose, rhmnose in major amnounts, other have only glucose
and rhmnose.
Ecology
Agromyces is common in soil.
2- Write short notes about the following:
a) production of antibiotics by Actinomycetes.
Actinomycets occupy a leading place among the antibiotic producing
groups of microorganisms. They have yielded more than 8000 antibiotics. Some of
these antibiotics are active only on bacteria, others on fungi, some are active on
viruses and phages while others are active on tumors. Some of antibiotics are said
to be a broad spectrum type, able to repress the growth of both bacteria and
fungi or of bacteria, rickettsiae and larger viruses. Some have a narrow antibiotic
spectrum, active against Gram-positive bacteria or mycobacteria or yeast-like
organisms.
Among the antibiotic producing actinomycetes, the genus Streptomyces
occupies a leading place. Streptomyces griseus and Streptomyces lavendula are
characterized by the formation of large number of different antibiotics.
====================================================
b) relation of Actinomycets to Bacteria.
1- The diameter of the hyphae and spores of Actinomycetes are much small
and are close to those of bacteria ( 0.5-1.0 u).
2- Actinomycetes are prokaryotes, they have no nuclear memberane.
3- The cell wall of actinomycets do not contain chitin or cellulose. The cell wall
chemically of bacterial type.
4- Motile forms of actinomycetes have flagella of the bacterial type.
5- Some actinomycetes are strickly anaerobic similar to anaerobic bacteria.
6- Some actinomycets are chemoautotrophic similar to chemoautotrophic
bacteria.
7- Actinomycetes are sensitive to the action of lysozyme and antibiotics which are
active with G+ve bacteria.
8- Actinomycetes cells like bacteria do not contain sterol.
9- Actinomycetes are subjected to attacks by numerous phages which are similar
in morphology and action to those attacking true bacteria.
10- Immunological studies showed relationship between actinomycetes and true
bacteria.
11- Actinomycetes synthesis lysine through diaminopimellic acid pathway similar
to that of true bacteria.
3- Complete:
a) Factors influencing Actinomycetes in soil are:
1-Soil type
2-Depth in the soil
3-Rhizosphere effect
5-Water contant and aeration
6 –Organic matter contant
4-pH value
7-Land use
b) Actinomycets morphology depends upon:
1-Examination of growing colonies
2-Fragmentation of the aerial and substrate mycelium
3-Branching of the aerial hyphae
4-Morphology of spore bearing organs
5-Morphology of spores
6-Morphology of spore surface
c) Cultural characteristics of Actinomycets depends upon:
1-Color of aerial mycelium
2-Color of substrate mycelium
of diffusible pigments
4-Melanin pigments
d) The criteria used for the description and classification of
Actinomycets are:
1-Morphological properties
2-Cultural characteristics
3-physiological and biochemical characteristics
wall composition 5-Antibiotic production
3-Color
4-Cell