microbiology Flashcards
Name the causal agent of necrotic enteritis in broiler (meat) chickens and list three of its morphological or physiological features (2.5 marks)
The causal agent of NE is Clostridium perfringens
• Morphological/ physiological Features (any of the following):
o Gram positive anaerobe (rod shaped)
o Spore forming – forms endospores (v resistant, dormant)
o Motile, use type IV pilli (kind of like pulling yourself along with fishing rod)
o Optimal growth pH 6-8
o 5 toxogenic (toxin types) A to E
List and describe the major predisposing factors that can elicit a necrotic enteritis outbreak in a broiler chicken flock.
• High Protein in diet
o If you don’t get the energy: protein ratio right, birds tend to consume too much protein. Increased protein, and N content is used as a nutritional substrate by these bacteria. They are already present in intestinal tract, but now can proliferate to higher numbers
o Also, high N makes chicken drink more, this leads to watery faecal matter. Being high in N it is a perfect medium for the bacteria grow, and then be ingested via chicken beaks
o High protein diet also raises pH in the gut to an optimum level for the bacteria, allowing proliferation
• Viscous diet
o If fed wheat and barley… Chickens lack enzymes to break down whole grains, therefore they make gut contents sticky, and slow transit time. This gives bacteria time to proliferate, as well as giving them a nutritional substrate
• Coccidiosis
o Elmeria parasites cause it
o Cause pre existing mucosal damage, and holes in the gut. Makes the gut more vulnerable for rapid proliferation of C. Perfringens and toxin production
o Causes increased mucus production, a rich CHO source, and nutritional substrate
o Increased transit time
collembola (springtails) - 2 features
eversible tubular appendage(the collopore)
Tail like appendage (furcula) - folded beneath the body used for jumping
collembola feeding
detritivores and microbiovores. found in leaf litter
eg of collembola - and description of effect
lucerne flea. pest species. eggs hatch on soaking autumn rains. Pests of broad leaf plants such as lucerne and clover
Insect anatomy
head, thorax, abdomen 2 compound eyes, 3 simple eyes (ocelli) antennae 3 pairs of legs up to 2 pairs of wings
exoskeleton insects
composed of plates (sclerites), separated by external grooves (sutures)
Membraneous areas separate plates so they can articulate/ flex body
insect eyes composed of
many repeating units (ommatidia), each has lens and crystalline cone. Light converges to structure called rhabdom (long) has light sensitive cells - retinula
Digestive system - insects
foregut, midgut, hind gut
Circulatory system
open system, haemolymph pumped forward by hearts to aorta, haemolymph in cavity. Expand/ contract. No function in respiration. Doesn’t carry co2, o2
Nervous system -
dorsal brain, ventral nerve cord, and ganglia (not all nervous activity in brain, some in ganglia)
Respiratory system - insects
- Tracheal system
- Spiracles microscopic openings on the sides of insects body
- gases enter and move through tracheoles (pipes) which extend to every cell in the body. Distribute respiratory gases directly
Spiracles. Where are they?
Occur on 2nd and 3rd thoracic segments and most abdominal segments (along the side of the insects body)
What are the two main internal structures of respiratory system?
Trachea and air sacs
Name of gradual metamorphosis
hemimetabola
Name of complete metamorphosis
holometabola
Differences between complete and gradual metamorphosis
Hemimetabola:
- Immature stages resemble adults
-IN most species immature stages and adults feed on same food
Holometabola
- Immature stages are unlike adults
- In many species immature stages and adults feed on different foods and occupy different niches (eg aquatic v terrestrial)
- Number of instars (moulting periods) varies among species from 3 to many
- Resting pupal stage involves transformation to the adult
Locusts and grasshoppers V crickets and katydids
Locusts and grasshoppers have short antennae
Stage at which survey and control needed (locusts)
Not swarms, marching bands
Australian plague locust
large dark spot on hindwings
Odonata key
2 nearly equal pairs of large membraneous wings
Anisoptera - dragonflies V damselflies
wings spread at rest, wings held over body at rest
Phthiraptera
apterous, small and dorsally flattened. parasitic
What louse causes damage to agriculture?
sheep body louse
Sheep body louse
Transmission by body contact
populations resistant to pyrethroid insecticides
Isoptera
Soldiers - highly specialised for defense (specialised defense mechanisms such as mandibles)
Social system termites
eusocial, queen, king and sterile workers
Termite - effect on agriculture
forage via tunnels, major effect on soil fertility
Hemiptera
sucking mouthparts with palps absent
gradual metamorphosis
some species vectors of plant viruses
biocontrol of aphids, thrips and mites
Example of hemiptera
scale insects - hard waxy covering
Thysanoptera
assymetric piercing sucking mouthparts
wings narrow with fringed setae
gradual metamorphosis
Impact on ag thysanoptera
transmit viruses, e.gwestern flower thrips transmits tomato spotted wilt virus
DIptera
single pair of wings
club like halteres on metathorax (small back wings)
Descripe complete metamorphosis - Diptera
Fly egg –> fly larvae –> Fly pupa (resistant cocoon in which they transform). Mosquito was fairly similar but in water
Nematocera
elongated flies, thin body, thin segmented antennae (mosquitos)
Brachycera
reduced antennae. SHort, hard to see (includes house flies, fruit flies)
Lucilia cuprina - importance to ag
obligate parasite of sheep. attracted to sheep odours. after 1st moult can feed on flesh
Lepidoptera
- two pairs of membraneous wings covered in scales (only sps which smaug scales)
- mouthparts modified into sucking probiscus (highly coiled, long)
Bogong moth key
build fat reserves up to 60% of bodyweight before summer
Lepitoptera pests (helicoverpa sps) - significance to ag. & why they are effective pests
- cotton bollworm
-native bollworm
Feed on plants
Developed resistance to range of insecticides
Neuroptera
-Two pairs of wings with numerous cross veins
-Larvae with distinctive sucking jaws
Biocontrols of aphids, thrips
Siphonaptera
fleas
- laterally flattened
Coleoptera
- elytra
- mandibulate mouthparts
Wood boring beetlyes
damage trees
Coleoptera effect on ag
estimated 1/3 of grain crop lost in storage. evolved resistance to insecticide
Hymenoptera
- mandibulate mouthparts
- two pairs of membraneous wings
- abdomen constricted between segments 1 and 2
Sawflies - hymenoptera
larvae resemble caterpillar but legs lack crochets (prolegs)
Bees feed on
pollen and nectar. and provide nectar and pollen to offspring
Wasps
parasitoid wasps major source of biocontrol
Ants (formicidae)
elbowed antennae and 1-2 segmented waist
Ants social
eusocial. Reproductive caste winged. Queen. Eggs mature into diploid sterile workers or reprodutive female or haploid males (haplodiploidy)
Ants importance ag
soil engineers, sometimes pest
