SOIL AND AIR AS ENVIRONMENTS OF MICROORGANISMS Flashcards
(169 cards)
1
Q
is an essential component of the biosphere
A
soil
2
Q
Soil is an essential component of the
A
biosphere
3
Q
depend on soil as a nutrient source and as a solid
surface matrix for growth and development.
A
terrestrial organisms
4
Q
Terrestrial organisms
such as __ and __depend on soil as a nutrient source and as a solid
surface matrix for growth and development
A
plants
animals
5
Q
Terrestrial organisms
such as plants and animals depend on soil as a (2)
A
nutrient source
solid surface matrix
6
Q
Terrestrial organisms
such as plants and animals depend on soil as a nutrient source and as a solid
surface matrix for (2)
A
growth
development
7
Q
Biological and biochemical
processes that occur in soils, which are mediated by
A
soil biota
8
Q
processes that occur in soils, which are mediated by soil biota, are important
for life on land to be sustainable.
A
biological
biochemical
9
Q
s also a favorable habitat for the growth
of various microorganisms
A
soil
10
Q
A handful of __contains a variety of
microorganisms in both number and kind.
A
soil
11
Q
microorganisms present in soil
A
viruses
bacteria
protozoa
algae
fungi
12
Q
Some of these microbes are involved in vital soil
processes such as
A
nutrient cycling
storage
support to plant growth
13
Q
is affected by different physical and chemical factors
A
soil microflora
14
Q
factors that affects soil microflora
A
pH
oxygen tension
carbon and energy source
15
Q
is a reservoir of microorganisms
A
air
16
Q
s a reservoir of microorganisms, but with little if any multiplication,
as it does in soil and water
A
air
17
Q
are accidental wanderers
flown from different sources and may occur as aerosols, attached to dust
particles or as free-floating bodies surrounded by films of dried organic or
inorganic materials.
A
airborne microorganisms
18
Q
airbone microorganisms are what
A
accidental wanderers
19
Q
Airborne microorganisms are accidental wanderers
flown from different sources and may occur as (3)
A
aerosols
attached to dust particles
free-floating bodies surrounded by films of dried organic or inorganic materials
20
Q
Some airborne microorganisms have special attributes
which permit continued survival in the said environment. However, many
cease ___activity until they are deposited again in a suitable
environment.
A
metabolic
21
Q
Viable airborne microorganisms can be monitored using a
variety of methods including (2)
A
sedimentation
impingement in liquids
22
Q
In this
exercise, the sedimentation method using ___plates technique will be
used to compare the number and types of airborne microorganisms present
in different intramural and extramural environments.
A
gravity
23
Q
culture media used in quantifying microorganisms in soil
A
Plate Count Agar (PCA)
Yeast Glucose
Chloramphenicol Agar (YGCA)
Nutrient Agar (NA)
24
Q
microbiological growth medium used to estimate the total number of viable bacteria in a sample
A
plate count agar
25
PCA is commonly used in what
food safety
water quality testing
26
YGCA Agar stands for
Yeast Extract Glucose Chloramphenicol Agar
27
It is a selective medium used for the enumeration and isolation of yeasts and molds, particularly in dairy products
YGCA Agar
28
component of YGCA that Inhibits bacterial growth, allowing only yeasts and molds to thrive.
chloramphenicol
29
is a widely used general-purpose growth medium in microbiology. It supports the growth of a broad range of non-fastidious microorganisms, meaning bacteria that do not require special nutrients to thrive
Nutrient Agar
30
is a nutrient-rich medium used for the cultivation of yeasts and molds. It contains peptone water and yeast extract, which provide essential nitrogen, vitamins, and growth factors for microbial development.
Peptone Yeast Agar (PYA)
31
is a specialized microbiological medium used for the isolation and cultivation of actinomycetes, particularly species like Streptomyces.
Glycerol Casein Agar (GCA)
32
It contains casein as a nitrogen source and glycerol as a carbon source, promoting the growth of actinomycetes while inhibiting unwanted bacteria.
Glycerol Casein Agar
33
An antifungal agent that suppresses yeast and mold growth, ensuring selective isolation of actinomycetes.
Nystatin in GCA
34
is a widely used medium for the cultivation of fungi, yeasts, and molds, particularly in food microbiology and environmental studies.
Potato Dextrose Agar
35
When supplemented with 50 ppm rose bengal and 100 ppm streptomycin, it becomes a selective medium that enhances fungal isolation while inhibiting bacterial growth.
PDA
36
A dye that restricts the spread of rapidly growing fungi, allowing for better colony differentiation
Rose bengal (50 ppm)
37
An antibiotic that suppresses bacterial contamination, ensuring selective fungal growth in PDA
Streptomycin
38
. Weigh and place dried 2g of each soil sample in a ____
beaker
weighing paper
39
Add 20 mL ___water and mix in a falcon tube. For samples that are
not mixing well, you may centrifuge them at low to medium speed for
20-30 minutes.
distilled
40
Add __mL distilled water and mix in a falcon tube. For samples that are
not mixing well, you may centrifuge them at low to medium speed for
20-30 minutes.
20
41
Weigh and place dried __g of each soil sample in a beaker/weighing
paper
2g
42
Weigh and place dried 2g of each __sample in a beaker/weighing
paper
soil
43
Add 20 mL distilled water and mix in a __tube. For samples that are
not mixing well, you may centrifuge them at low to medium speed for
20-30 minutes.
falcon
44
Add 20 mL distilled water and mix in a falcon tube. For samples that are
not mixing well, you may ___them at low to medium speed for
20-30 minutes.
centrifuge
45
Add 20 mL distilled water and mix in a falcon tube. For samples that are
not mixing well, you may centrifuge them at ___ to ___speed for
20-30 minutes.
low
medium
46
Add 20 mL distilled water and mix in a falcon tube. For samples that are
not mixing well, you may centrifuge them at low to medium speed for
___ minutes.
20-30
47
Allow the samples to stand for __ minutes for the soil-water paste to
reach equilibrium.
15
48
Allow the samples to stand for 15 minutes for the soil-water paste to
reach ___.
equilibrium
49
Allow the samples to stand for 15 minutes for the ___-___ paste to
reach equilibrium.
soil
water
50
Allow the samples to stand for 15 minutes for the soil-water ___to
reach equilibrium.
paste
51
Measure the samples’___ using a digital pH meter (4:43 onwards). Make
sure that the digital pH meter is calibrated prior to use. For calibration
at pH 7 and pH 4, watch segments 1:19 to 4:40.
pH
52
Measure the samples’ pH using a ___ (4:43 onwards). Make
sure that the digital pH meter is calibrated prior to use. For calibration
at pH 7 and pH 4, watch segments 1:19 to 4:40.
digital pH me
53
Measure the samples’ pH using a digital pH meter (4:43 onwards). Make
sure that the digital pH meter is __prior to use. For calibration
at pH 7 and pH 4, watch segments 1:19 to 4:40.
calibrated
54
Measure the samples’ pH using a digital pH meter (4:43 onwards). Make
sure that the digital pH meter is calibrated prior to use. For calibration
at pH ___ and pH ___, watch segments 1:19 to 4:40.
7
4
55
. Determine the weight of ____ previously dried at 100
°C for 24 hours for soil moisture content measurement
aluminum dishes
cans
56
. Determine the weight of aluminum dishes/cans previously dried at ___
°C for 24 hours
100oC
57
. Determine the weight of aluminum dishes/cans previously dried at 100
°C for __hours
24
58
Add ___ of moist soil to a dish and determine total weight.
~10g
59
Add ~10g of moist soil to a dish and determine ____ ___.
total weight
60
Place samples in an ___set at 100 °C and weigh after 24hrs. or until
a constant weight can be read repeatedly.
oven
61
Place samples in an oven set at ___°C and weigh after 24hrs. or until
a constant weight can be read repeatedly.
100
62
Place samples in an oven set at 100 °C and weigh after ___. or until
a constant weight can be read repeatedly.
24
63
Place samples in an oven set at 100 °C and weigh after 24hrs. or until
a ___weight can be read repeatedly.
constant
64
Calculate ___ ___weight of soil sample by subtracting the weight of
the aluminum dish to the constant weight of soil sample.
oven dry weight
65
Determine the moisture content of the soil by using the following
formula:
fresh weight - oven dry weight / oven dry weight *100
66
Weigh __g of soil and add to 10mL sterile deionized water. Shake the
suspension vigorously. This will be the soil suspension
1
67
Weigh 1g of soil and add to 10mL __ ___ water. Shake the
suspension vigorously. This will be the soil suspension
sterile deionized
68
Weigh 1g of soil and add to __mL sterile deionized water. Shake the
suspension vigorously. This will be the soil suspension
10 mL
69
Weigh 1g of soil and add to 10mL sterile deionized water. Shake the
suspension ___. This will be the soil suspension
vigorously
70
Weigh 1g of soil and add to 10mL sterile deionized water. Shake the
suspension vigorously. This will be the __ ___
soil suspension
71
Do serial dilutions using __ tubes of 9mL of sterile distilled water
as diluent labelled 10-1 to 10-4.
4
72
serial dilution of tubes to perform pour plate method for bacterial
colony counting.
10^-3 to 10^-4
73
. For actinomycetes: Spread plate 0.1 ml of each of the three tubes onto
sterile agar plates containing ___. Incubate plates at
room temperature in an inverted position for 2 weeks.
GCA
74
. For ___: Spread plate 0.1 ml of each of the three tubes onto
sterile agar plates containing Glycerol Casein Agar. Incubate plates at
room temperature in an inverted position for 2 weeks.
actinomycetes
75
. For actinomycetes: ___ plate___ml of each of the three tubes onto
sterile agar plates containing Glycerol Casein Agar. Incubate plates at
room temperature in an inverted position for 2 weeks.
spread
0.1
76
For ___: Spread plate 0.1 mL of tubes labeled 10-1 and 10-2 onto
sterile agar plates containing Potato Dextrose Agar with Rose Bengal
and Streptomycin. Incubate plates at room temperature in an inverted
position for 1-2 weeks.
fungi
77
For fungi: ___ plate ___mL of tubes labeled 10-1 and 10-2 onto
sterile agar plates containing Potato Dextrose Agar with Rose Bengal
and Streptomycin. Incubate plates at room temperature in an inverted
position for 1-2 weeks.
spread
0.1
78
For fungi: Spread plate 0.1 mL of tubes labeled ___ and ___onto
sterile agar plates containing Potato Dextrose Agar with Rose Bengal
and Streptomycin. Incubate plates at room temperature in an inverted
position for 1-2 weeks.
10-1
10-2
79
For fungi: Spread plate 0.1 mL of tubes labeled 10-1 and 10-2 onto
sterile agar plates containing what media
Incubate plates at room temperature in an inverted
position for 1-2 weeks.
Potato Dextrose Agar with Rose Bengal
and Streptomycin.
80
After the prescribed incubation periods, take note of the ___ of
growing bacteria (surface appearance, pigmentation, etc.) and
actinomycetes (chalky, leathery, brittle colonies).
morphology
81
. Bacteria: Estimate the number of soil bacteria from the plates. Most
accurate values are obtained from plates with what counts
30 to 300
82
Actinomycetes: Determine the number of actinomycetes using GCA
plates with ___colonies showing characteristic flat and compact
appearance which adhere tenaciously to the surface of the agar.
30 to 300
83
Soil fungi: Count the number of colonies growing on the PDA plates.
Select plates with ___ colonies. A preliminary count may be done
after two days since the plates may become overgrown.
15 to 150 colonies
84
Compute the number of soil fungi, bacteria, and actinomycetes in terms
of colony forming units (CFU) per gram of soil (oven dry weight basis)
using either of the formulas given below:\
1. when two consecutive ten-fold dilutions have valid counts:
CFU/ g = (ΣC) (FW) / [(1 x n1) + (0.1 x n2)] (d) (Vp) (ODW)
where
where:
ΣC = sum of all colonies in all plates counted
FW = wet weight of soil
n1 = number of plates in lower dilution counted
n2 = number of plates in the next higher dilution counted
d = dilution from which the first counts were obtained
Vp = volume plated, and
ODW = dry weight of soil
85
When only one of the dilutions has counts within the countable
range:
CFU/g = (average number of colonies) (df) (FW) / (Vp) (ODW)
wherewhere:
df = reciprocal of the dilution
86
Reagents and Culture Media for gravity/settle plate method
Plate count agar (PCA) plates with 1000 units/ mL nystatin
* Potato dextrose agar (PDA) plates with 50 ppm rose bengal and 100
ppm streptomycin
* Nutrient agar (NA) plates
87
Refers to indoor environments, such as hospitals, laboratories, food processing facilities, and clean rooms.
intramural settings
88
. In these settings, microbial enumeration helps monitor air quality, detect contamination risks, and ensure compliance with hygiene standards.
intramural settings
89
Refers to outdoor environments, such as agricultural fields, urban areas, and industrial sites.
extramural setting
90
the settle method is used to study airborne microbial populations, environmental pollution, and the spread of bioaerosols.
extramural setting
91
compute moisture content given
fresh weight (g) = 8.1
oven dry weight (g) = 7
15.71%
92
compute bacterial count for spread plate on PYA
10-2 204
10-3 30
fresh weight (g) = 8.1
oven dry weight = 7
= 2.46x105 CFU/g ODW
93
compute actinomycetes for spread plate on GCA with nystatin
10-1 87
10-2 17
fresh weight (g) = 8.1
oven dry weight = 7
= 1.01x10
4 CFU/g ODW
94
compute fungal count on PDA
10-1 38
10-2 1
10-3 0
fresh weight (g) = 8.1
oven dry weight = 7
= 4.4x103 CFU/g ODW
95
rationale to see when there is relatively low growth in laboratory room
Environmental factors and the selective properties of the chosen culture
media used influence the microbial air quality observed through the plates.
Indoor environments with strict contamination control, such as laboratory
rooms, generally exhibit lower microbial counts across all media types. The
low counts on Plate Count Agar (PCA), a general-purpose medium, indicate a
limited presence of culturable heterotrophic bacteria. Yeast Glucose
Chloramphenicol Agar (YGCA), which is selective for fungi due to including
chloramphenicol to inhibit bacterial growth, shows slightly higher counts,
reflecting the potential presence of airborne fungal spores. Nutrient Agar (NA)
exhibits the highest counts in the laboratory setting, suggesting that the
prevailing conditions may favor the growth of certain bacterial species
detectable on NA but not as readily on PCA.
96
rationale why comfort rooms have high CFU
Environments such as comfort rooms, with higher human occupancy and
activity levels, demonstrate increased microbial diversity and load. The
elevated counts on PCA indicate more common environmental bacteria shed
from human skin and respiratory droplets. YGCA counts are also higher
compared to the laboratory room, indicating a potential increase in fungal
contamination due to moisture and humidity levels often associated with
comfort rooms. NA supports a relatively high microbial load, suggesting that
comfort rooms provide a conducive environment for a broader range of
bacterial species
97
rationale why balcony has the highest CFU
The balcony, as an outdoor environment, exhibits the
highest microbial counts across all media types due to constant exposure to
external microbial sources and fluctuating environmental conditions.
98
In general, which microbial group/s (other bacteria, actinomycetes, fungi)
is/are expected to dominate in each soil type ? Justify your answer
Bacteria are dominant throughout the soil types because of high abundance
and metabolic versatility; thus, allowing these species to diversely thrive
under several conditions. These specific soil types can favor other groups of
microbes. A great example would be soil with low pH can be dominant of
fungal organisms, as these species thrive in acidic environments.
Actinomycetes are filamentous bacteria that survive in aerated and drier soils.
Thus, every microorganism (i.e. bacteria, actinomycetes, and fungi) are
expected to live more abundantly than the said counterparts.
99
How do pH and moisture content affect the predominant microbial types
in different soil types?
Soil pH and moisture content critically influence microbial community
composition and activity across soil types. pH primarily determines bacterial
diversity and dominance, with optimal microbial diversity typically peaking
near a soil's native pH level, as deviations disrupt nutrient availability and
cellular functions, favoring acid-tolerant genera in acidic conditions. Moisture
modulates microbial activity and substrate utilization, with moderate levels
(~60% water-holding capacity) maximizing labile carbon processing and
organic matter decomposition, while extreme moisture reduces gas exchange
and nutrient diffusion, altering functional gene expression in nitrogen and
methane cycles. These factors interact with soil type—clay-rich soils buffer pH
shifts, while sandy soils amplify moisture effects—shaping distinct microbial
assemblages adapted to local physicochemical conditions.
100
3. What is the function of Rose Bengal in Potato Dextrose Agar?
Rose Bengal is an eosin-like dye used in Potato Dextrose Agar (PDA) to inhibit
fast-growing fungi, preventing overgrowth and allowing for the isolation and
differentiation of slower-growing species such as yeasts and molds. It also has
antimicrobial properties, which prevent bacterial contamination during fungal
culture. The dye's pink tint helps to distinguish between fungal colonies, which
is beneficial for identifying individual fungi or yeasts in mixed cultures.
101
. Differentiate actinomycetes from other members of the domain
Eubacteria. Why are they abundant in soil?
Actinomycetes are distinct from other Eubacteria due to their unique
morphological and metabolic traits. Actinomycetes are characterized by their
filamentous growth as they form branching hyphae (resembling fungal
mycelia) and spores while most Eubacteria lack this structural complexity.
Moreover, Actinomycetes have high G+C DNA ratio (>50%) compared to
many Eubacteria (E. coli has about 50%). Lastly, actinomycetes have
metabolic capabilities such as decomposition of complex polymers (e.g.
cellulose, lignin, chitin), antibiotic production, and nitrogen fixation that are
rare or not present in other members of Eubacteria.
As for its abundance, Actinomycetes dominate in decomposing plant and
animal debris in the soil releasing nutrients and improving soil fertility in the
process. Additionally, they thrive in diverse soils from acidic (pH 4.0-4.3) to
neutral conditions. Actinomycetes are also able to resist stress such as in dry
or nutrient-poor environments. Lastly, antibiotic production in Actinomycetes
suppresses competing microbes in the soil reducing interspecies competition.
102
When is the Most Probable Number method preferable to be used over
Standard Plate Count in estimating population of microorganisms?
The Most Probable Number (MPN) is preferred over Standard Plate Count
(SPC) because MPN is mostly used in counting low microbial concentrations.
SPC is better used in higher concentrations. MPN offers better results in
estimating population size, which is more useful in certain applications.
103
The Most Probable Number (MPN) is preferred over Standard Plate Count
(SPC) because MPN is mostly used in counting low microbial concentrations.
SPC is better used in higher concentrations. MPN offers better results in
estimating population size, which is more useful in certain applications.
Under certain conditions, microbial load may be greater in intramural
environments. High humidity and poor ventilation can lead to airborne
microorganisms, while extramural environments have better air circulation.
Stable and warm temperatures in intramural environments can facilitate
microbial proliferation, and high human occupancy can also contribute to this
due to shedding of skin cells and respiratory droplets. Outdoor air also carries
microorganisms. Outdoor air can also contain microorganisms, but intramural
environments can concentrate particular types, especially if conditions favor
their growth. Microbial loads may be lower in well-ventilated and regularly
cleaned indoor spaces than polluted outdoor environments.
104
indication of the acidity or alkalinity of soil and is measured in
pH units
105
As the amount of hydrogen ions in the soil increases, soil pH ___ thus becoming more ___.
decreases
acidic
106
From pH 7 to 0 the soil is increasingly more ___
acidic
107
from pH 7 to 14 the soil is increasingly more
___
alkaline or basic
108
can be determined by mixing soil sample with water and then
measuring the resulting aqueous solution.
soil pH
109
soil pH can be determined by mixing soil ___with water and then
measuring the resulting aqueous solution.
sample
110
pH affects ___of minerals or nutrients.
solubility
111
__ of the 17 essential plant nutrients are obtained from the soil.
14
112
minerals and nutrients are more soluble or available in ___ soils than in neutral
or slightly ___soils.
acid
alkaline
113
most available in soil with a pH range centered around 6.5.
phosphorus
114
Phosphorus most available in soil with a pH range centered around
6.5
115
pH of soils that can have high concentrations of
soluble aluminum, iron and manganese which may be toxic to the growth of
some plants
extremely and strongly acid (pH 4-5)
116
Extremely and strongly acid soils (pH 4.0-5.0) can have high concentrations of
(3) which may be toxic to the growth of
some plant
soluble aluminum
iron
manganese
117
pH around promotes the most ready availability of plant nutrients
6 to 7
118
* influence plant growth by its effect on activity of beneficial microorganisms.
pH
119
Bacteria that decompose soil organic matter are hindered in strong __ soils.
acid
120
* This prevents ___ ___from breaking down, resulting in an accumulation
of organic matter and the tie up of nutrients, particularly nitrogen, that are held
in the organic matter.
organic matter
121
* This prevents organic matter from breaking down, resulting in an accumulation
of organic matter and the tie up of nutrients, particularly ___, that are held
in the organic matter.
nitrogen
122
what pH of soils is there major nutrient deficiences
strongly acidic
123
pH of soil for optimum pH range for plant growth
neutral
124
pH of soil with trace element deficiencies
alkaline
125
___ availability becomes a problem on alkaline soils
iron
126
pH with reduced soil microbial activity
5.5
127
Soils tend to become acidic as a result of (3)
rain water leaching basic ions
CO2 from decomposing organic matter and root respiration dissolving in soil water to form a weak organic acid
formation of strong organic and inorganic acids from decaying organic matter, oxidation of ammonium and sulfur fertilizers
128
Soils tend to become acidic as a result of:
___ leaching away basic ions (calcium, magnesium, potassium and sodium);
rainwater
129
Soils tend to become acidic as a result of:
(1) rainwater leaching away basic ions such as
calcium
magnesium
potassium
sodium
130
Soils tend to become acidic as a result of:
___ from decomposing organic matter and root respiration dissolving
in soil water to form a weak organic acid;org
carbon dioxide
131
Soils tend to become acidic as a result of:
(2) carbon dioxide from decomposing ___ ___ and root respiration dissolving
in soil water to form a weak organic acid;
organic matter
132
(2) carbon dioxide from decomposing organic matter and ___ ___ dissolving
in soil water to form a weak organic acid
root respiration
133
(2) carbon dioxide from decomposing organic matter and root respiration dissolving
in soil water to form a ___ ___ ___;
weak organic acid
134
Soils tend to become acidic as a result of:
(3) formation of strong organic and inorganic acids, such as ___ ____
from decaying organic matter and oxidation of ammonium and sulfur fertilizers.
sulfuric
nitric acid
135
(3) formation of strong organic and inorganic acids, such as nitric and sulfuric acid,
from decaying organic matter and ___of ammonium and sulfur fertilizers.
oxidation
136
(3) formation of strong organic and inorganic acids, such as nitric and sulfuric acid,
from decaying organic matter and oxidation of __ and ___fertilizers.
ammonium
sulfur
137
entire quantity of water in the ground’s
pores or on its surface
soil moisture
138
The moisture
content of soil depends on such factors as (3)
weather
type of land
plants
139
Soil moisture affects (3)
content of air, salinity, amount of toxic substances
ground structure and thickness
temperature and heat capacity of groun
140
optimum moisture content of soil
30% on silt loam
141
low moisture content of soil is considered as
sand
142
medium moisture content of soil is considered as
loam
143
high moisture content of soil is considered as
clay
144
means how much water the soil
can hold after the excess drains
off.
field capacity
145
Soil is also a favorable habitat for the growth of various microorganisms.
These include
viruses
bacteria
protozoa
algae
fungi
146
Some of these microbes are involved in vital soil processes such as __ ___and storage as well as support to plant growth
nutrient cycling
147
is affected by different physical and chemical factors
soil microflora
148
Factors affecting soil microflora
pH
oxygen tension
carbon and energy source
149
Factors such
as pH, oxygen tension, carbon and energy source, all affect the (4) of microorganisms
diversity
density
distribution
activity
150
are the most numerous among the cultivable microorganisms
from soil.
bacteria
151
a gram of soil may contain up to
1x10^8
152
___of the total biomass in the soil is bacteria
70-90%
153
are second only to bacteria in the soil
fungi
154
which inhabit extreme environments—make up a substantial
fraction of soil microorganisms
archaea
155
In terms of function, soil bacterial groups may
be subdivided into four categories (Ingham,
2019)
decomposers
mutalists
pathogens
litotrophs/chemoautotrophs
156
, including roots, leaves, and other secretions - primary source of soil carbon to supply
microbes in the soil
plant residues
157
plant residues, including __ , ___, and other secretions - primary source of soil carbon to supply
microbes in the soi
roots
leaves
158
) plant residues, including roots, leaves, and other secretions - primary source of soil __ to supply
microbes in the soi
carbon
159
release nutrients through metabolic activities, supporting soil development, promoting
plant growth, and maintaining the stability of soil carbon cycling;
microorganisms
160
through what processes microorganisms can directly affect plant growth and development.
mycorrhizal symbiosis
releasing hormones
stress signals
161
are a large group of bacteria that
grow as hyphae like fungi.
actinomycetes
162
actinomycetes hyphae are much more ___
smaller
163
responsible for the characteristically “earthy”
smell of freshly turned, healthy soil.
actinomycetes
164
actinomycetes are important in degrading __ compounds
recalcitrant (hard to decompose)
165
especially important in degrading recalcitrant
(hard-to-decompose) compounds, such as c
chitin
cellulose
166
are more important in degrading these
compounds at low pH.
fungi
167
A number of antibiotics are produced by
actinomycetes such as
streptomyces
168
What can soil microbes do to
the soil?
nutrient cycling
decomposition of organic matter
water movement
plant growth promotion
disease suppression
169
is a reservoir of microorganisms, but with little if any multiplication, as it
does in soil and water.
air
