Question

BIOL2516K Spring 2020 Week 6 Results and Homework Name Melanie Couard Urea Phenylalanine color + or - Ex. 12 Data Sheet Gelatin hydrolase, urease, and phenylalanine deaminase results Gelatin Gelatin or any liquid color + or color present? yes or no uninoculated tube NO light orange Enterobacter aerogenes yellow NO I- Jorange - yellon Pseudomonas aeruginosa yes + - prange - brange - Escherichia coli INO yellow - Proteus vulgaris yes t Pink green SIM results HS production color + or - Indole color Motility describe growth pattern Nellow uninoculated tube beige NO Enterobacter aerogenes - brown Black Escherichia coli NO black - Tred + Proteus vulgaris Black t redt Ex. 12 Questions 1. Which species of bacteria produce the enzyme tryptophanase? CO + proteus vulgaris auduce the enzyme 2. Which species of bacteria produce the enzyme phenylalanine deaminase? Cryptophanas proteus vulgaris produces the enzyme phenylaline deaminase

Answer 1

(1).Escherichia coli produces indole from the amino acid tryptophan by action of the enzyme tryptophanase, and this is a distinguishing feature of E. coli from other enteric bacteria.

(2).Proteus, Providencia, and Morganella species produce deaminases that generate -keto acids from amino acids. The -keto acid products are detected by the formation of colored iron complexes, raising the possibility that the enzyme functions to secure iron for these species, which do not produce traditional siderophores.

(3).Urease is observed in Helicobacter sp., including all Helicobacter pylori isolated from gastritis patients . Urease is an enzyme synthesized by pathogenic mycobacteria like Mycobacterium tuberculosis and Mycobacterium bovis . It was observed that anaerobic clostridia are capable of urea hydrolysis.

(4). (a).

  P. aeruginosa is a facultative anaerobe, as it is well adapted to proliferate in conditions of partial or total oxygen depletion. This organism can achieve anaerobic growth with nitrate or nitrite as a terminal electron acceptor. When oxygen, nitrate, and nitrite are absent, it is able to ferment arginine and pyruvate by substrate-level phosphorylation.Adaptation to microaerobic or anaerobic environments is essential for certain lifestyles of P. aeruginosa, for example, during lung infection in cystic fibrosis and primary ciliary dyskinesia, where thick layers of lung mucus and bacterially-produced alginate surrounding mucoid bacterial cells can limit the diffusion of oxygen. P. aeruginosa growth within the human body can be asymptomatic until the bacteria form a biofilm, which overwhelms the immune system. These biofilms are found in the lungs of people with cystic fibrosis and primary ciliary dyskinesia, and can prove fatal.

Cellular cooperation :-

P. aeruginosa relies on iron as a nutrient source to grow. However, iron is not easily accessible because it is not commonly found in the environment. Iron is usually found in a largely insoluble ferric form.Furthermore, excessively high levels of iron can be toxic to P. aeruginosa. To overcome this and regulate proper intake of iron, P. aeruginosa uses siderophores, which are secreted molecules that bind and transport iron. These iron-siderophore complexes, however, are not specific. The bacterium that produced the siderophores does not necessarily receive the direct benefit of iron intake. Rather, all members of the cellular population are equally likely to access the iron-siderophore complexes. Members of the cellular population that can efficiently produce these siderophores are commonly referred to as cooperators; members that produce little to no siderophores are often referred to as cheaters. Research has shown when cooperators and cheaters are grown together, cooperators have a decrease in fitness, while cheaters have an increase in fitness.The magnitude of change in fitness increases with increasing iron limitation. With an increase in fitness, the cheaters can outcompete the cooperators; this leads to an overall decrease in fitness of the group, due to lack of sufficient siderophore production. These observations suggest that having a mix of cooperators and cheaters can reduce the virulent nature of P. aeruginosa.

(b)

  Pseudomonas aeruginosa is an important bacterial pathogen, particularly as a cause of infections in hospitalized patients and revealed trends of increasing antimicrobial resistance. However, resistance to fluoroquinolone antibiotics has been reported in recent years as well. This cross-sectional study included a total of 932 clinical samples received from various departments of Central Referral Hospital, Gangtok from August 2005 to August 2008. The samples were cultured in 5% sheep blood agar and MacConkey agar at 37°C for 18–24 hours. The isolates were preliminarily identified as Pseudomonas spp. by biochemical and physiological tests, colony morphology, production of diffusible pigments, and a grape-like odour. Gram-negative bacilli with above-mentioned characteristic features were considered as P aeruginosa on the basis of a positive oxidase test, a triple sugar iron (TSI) agar reaction of alkaline over no change, growth at 42°C and production of bright-blue to blue green diffusible pigment on Mueller-Hinton agar. Non-pigmented isolates were identified as P. aeruginosa by the above-mentioned characters along with oxidation of glucose, but not disaccharides, hydrolysis of acetamide, and reduction of nitrates to nitrogen gas. One sample was collected from each patient. The susceptibility of P aeruginosa strains to ciprofloxacin (5 µg), ofloxacin (5 µg), levofloxacin (5 µg), norfloxacin (10 µg), and pefloxacin (5 µg) was studied by Kirby-Bauer disc diffusion method according to NCCLS (National Committee for Clinical and Laboratory Standards) criteria. Out of a total of 932 clinical samples received, 682 samples were pus, 125 were urine, 83 were blood, and 42 were sputum. Of them 268 (28.76%) were isolated having P aeruginosa strains [pus (196), urine (36), blood (24), and sputum (12)]. Two hundred and eight (77.61%) isolates were obtained from in-patients, while only 60 (22.39%) were from out-patients. Ciprofloxacin (47.76%) was found to be the most effective anti-pseudomonal agent followed by levofloxacin (44.78%). However, this difference was not significant (P>0.05). The susceptibility patterns of ciprofloxacin and levofloxacin were highly significant when analyzed with the susceptibility patterns of norfloxacin (23.88%), ofloxacin (20.90%), and pefloxacin (8.96%), (Chi-square: 225.75, p value <0.0001).