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
