潰瘍性結腸炎 (UC) 是一種原因不明的炎症性腸道疾病，治療原則是減輕炎症，但UC的病因有多種，一般消炎藥物如柳氮磺胺吡啶 (sulfasalazine) 等治療都是單靶向並有嚴重副作用，故副作用低、多靶向藥物是必要的。 / Cathelicidin 是一種抗菌抗炎的肽。事實上，鼠的 cathelicidin (mCRAMP) 直腸給藥能緩解小鼠 UC。為了提高療效及方便給藥，mCRAMP 編碼被導入乳酸乳球菌中。乳酸乳球菌是一種能抵抗胃酸的乳酸益生菌，因此口服亦能生產及傳送 cathelcidin 到大腸。 / 小鼠用含3% 葡聚醣硫酸鈉 (DSS) 的水7天以誘導UC。小鼠隨機分為十組，各接受每日一次的口服製劑：(1) 水，(2) DSS，(3, 4) DSS + 10¹° cfu 有或沒有 nisin 誘導的乳酸乳球菌，(5-8) DSS + 10⁸ 或 10¹° cfu有 (N4I) 或沒有 nisin 誘導的 mCRAMP 編碼乳酸乳球菌，(9) DSS + 0.5% 羧甲基纖維素鈉 (CMC-Na) 及 (10) DSS + 600 mg/kg懸浮於0.5% CMC-Na 的 sulfasalazine。 / 研究對 UC 預防效果時，小鼠同時接受 DSS 及治療。所有益生菌製劑中，只有 N4I 能降低中性粒細胞浸潤、脂質過氧化和炎症細胞因子表達，同時保護腸隱窩及黏膜分泌層結構，減少細胞凋亡及腸道菌群。相比之下，sulfasalazine 能抑制炎症但不能阻止結腸結構損傷。 / 進一步研究治療效果時，小鼠在炎症形成後接受四天治療。N4I 能促進結腸黏膜恢復，改善結腸和黏液分泌層的結構。這些作用可能通過刺激細胞增殖和抑制凋亡造成。相對地，sulfasalazine 對結腸組織重組沒有影響。 / 為了研究 mCRAMP 直接消炎作用，小鼠巨噬細胞 RAW 264.7 被脂磷壁酸和脂多醣刺激以模仿 UC 時細菌引起的炎症。mCRAMP 能減輕腫瘤壞死因子-α分泌及IκBα磷酸化並抑制核因子-κB (NF-κB) 活化，炎症酶如誘導型一氧化氮合酶和環氧合酶-2的表達也減少了。mCRAMP可能直接抑制細菌毒素與受體結合和/或直接抑制 NF-κB 產生消炎作用。 / 在研究 mCRAMP 修復黏膜的作用中，證實 mCRAMP 通過 G 蛋白偶聯受體依賴途徑和間接激活表皮生長因子受體、激活下游絲裂原活化蛋白激酶而促進細胞遷移、加速癒合。 / 總括而言，本研究首次顯示mCRAMP編碼乳酸乳球菌對 UC 有保護和治療作用，其抗炎、抗菌及促進黏膜修復作用來自乳酸乳球菌分泌的mCRAMP。多靶向的mCRAMP編碼乳酸乳球菌具有很大潛力，是一種比標準藥物 sulfasalazine 更好的治療結腸炎製劑。 / Ulcerative colitis (UC) is an idiopathic inflammatory bowel disease (IBD). The mainstay of drug treatment is to relieve inflammation. However the aetiology of UC is multi-factorial while most of the anti-inflammatory drugs, such as sulfasalazine, aim at single target with severe side effects. Therefore, a multi-targeted drug with low systemic toxicity is warranted. / Cathelicidin, a host defense peptide, shows anti-microbial and anti-inflammatory effects. Indeed intra-rectal administration of mouse cathelicidin (mCRAMP) alleviated murine colitis. To improve therapeutic efficacy and reduce inconvenience of administration, Lactococcus lactis (L. lactis) was constructed to encode cathelicidin. L. lactis is a lactic acid probiotic which could resist gastric acid and be able to produce and deliver cathelicidin to the colon when given orally. / Murine colitis was induced by 3% dextran sulphate sodium (DSS) given in drinking water for 7 days. Mice were given intragastrically with the following preparations once daily: (1) water, (2) DSS, (3, 4) DSS + 10¹° cfu L. lactis with or without nisin induction, (5-8) DSS + 10⁸ or 10¹° cfu mCRAMP-encoding L. lactis with (N4I) or without nisin induction, (9) DSS + 0.5% sodium carboxymethylcellulose (CMC-Na) and (10) DSS + 600 mg/kg sulfasalazine suspended in 0.5 % CMC-Na. / To study the preventive effects, mice received the above treatments together with DSS administration. N4I but not the other probiotic preparations suppressed inflammation by reducing neutrophil infiltration, lipid peroxidation and inflammatory cytokines expressions. Crypt structure and mucus-secreting layer were conserved together with the reduction of apoptosis and intestinal microbiota. In contrast, sulfasalazine could only suppress inflammation but not the destruction of colonic structure. / To further examine the therapeutic effects, mice received treatments for 4 consecutive days after the inflammation formation. Similarly, only N4I promoted colonic mucosal recovery and preserved colon structure and mucus-secreting layer. These actions are likely mediated through cell proliferation stimulation and apoptosis suppression. Again, sulfasalazine had no effects on colon tissue reconstitution. / The direct anti-inflammatory action of mCRAMP was also studied. Mouse macrophage RAW 264.7 cells were stimulated by lipoteichoic acid and lipopolysaccharide to mimic bacteria-induced inflammation during UC. mCRAMP prevented tumour necrosis factor-α secretion and IκBα phosphorylation followed by nuclear factor-κB (NF-κB) suppression. The inflammatory enzymes including inducible nitric oxide synthase and cyclooxygenase-2 were also reduced. It was postulated that mCRAMP might directly interact with the bacterial toxins to reduce receptor complex binding and/or reduce NF-κB suppression in macrophages. / The repairing action of mCRAMP on mucosal damage was studied in mouse colon cells. mCRAMP incubation reduced the wound size by promoting cell migration through the G-protein coupled receptor and epidermal growth factor receptor transactivation followed by the mitogen-activated protein kinases activation. / In conclusion, the present study demonstrates for the first time the protective and therapeutic roles of mCRAMP-encoding L. lactis in UC. It was the mCRAMP secreted from the probiotic to produce both anti-inflammatory and anti-bacterial actions and further promote mucosal repair. mCRAMP-encoding L. lactis is a multi-targeted agent for IBD. It has a great potential to be a new therapeutic agent better than sulfasalazine for the treatment of UC. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Wong, Ching Man. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 227-250). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Abstract --- p.i / Acknowledgement --- p.v / Table of Content --- p.vi / List of Abbreviations --- p.xiii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Ulcerative Colitis --- p.1 / Chapter 1.1.1 --- Overview --- p.1 / Chapter 1.1.2 --- Epidemiology --- p.2 / Chapter 1.1.3 --- Diagnosis --- p.2 / Chapter 1.1.3.1 --- Clinical Presentation --- p.2 / Chapter 1.1.3.2 --- Apparative Diagnostics --- p.3 / Chapter 1.1.3.3 --- Innovative Diagnostics in IBD --- p.4 / Chapter 1.1.4 --- Etiopathogenesis --- p.4 / Chapter 1.1.4.1 --- Genetic Predisposition --- p.4 / Chapter 1.1.4.2 --- Environmental Factors --- p.5 / Chapter 1.1.4.2.1 --- Life Style --- p.5 / Chapter 1.1.4.2.1.1 --- Smoking --- p.5 / Chapter 1.1.4.2.1.2 --- Diet --- p.6 / Chapter 1.1.4.2.1.3 --- Hygiene --- p.6 / Chapter 1.1.4.2.1.4 --- Psychological Stress --- p.6 / Chapter 1.1.4.2.1.5 --- Appendectomy --- p.7 / Chapter 1.1.4.2.2 --- Colonic Mucus --- p.7 / Chapter 1.1.4.2.3 --- Non-steroidal Anti-inflammatory Drugs (NSAIDs) --- p.7 / Chapter 1.1.4.3 --- Alteration of Intestinal Microbiota --- p.8 / Chapter 1.1.4.4 --- Immune Factors --- p.10 / Chapter 1.1.5 --- Existing Treatments --- p.10 / Chapter 1.1.5.1 --- 5-Aminosalicyclic Acid --- p.11 / Chapter 1.1.5.2 --- Corticosteroids --- p.12 / Chapter 1.1.5.3 --- Immunomodulators --- p.12 / Chapter 1.1.5.4 --- Surgical Management --- p.13 / Chapter 1.1.6 --- Emerging Treatments --- p.14 / Chapter 1.1.6.1 --- Antibiotics --- p.14 / Chapter 1.1.6.2 --- Probiotics --- p.14 / Chapter 1.1.6.3 --- Nicotine Patches --- p.14 / Chapter 1.1.6.4 --- Butyrate --- p.14 / Chapter 1.1.6.5 --- Biological Therapies --- p.15 / Chapter 1.1.7 --- Risk of Colorectal Cancer --- p.17 / Chapter 1.2 --- Cathelicidin --- p.17 / Chapter 1.2.1 --- Cathelicidin Family --- p.17 / Chapter 1.2.2 --- Actions and Possible Mechanisms --- p.19 / Chapter 1.2.3 --- Cathelicidin in Ulcerative Colitis --- p.20 / Chapter 1.3 --- Probiotics --- p.21 / Chapter 1.3.1 --- Lactic Acid Bacteria --- p.21 / Chapter 1.3.2 --- Definition of Probiotics --- p.22 / Chapter 1.3.3 --- Possible Mechanisms of Action of Probiotics --- p.23 / Chapter 1.3.3.1 --- Mucous Layer --- p.23 / Chapter 1.3.3.2 --- Host Cell Antimicrobial Peptides --- p.25 / Chapter 1.3.3.3 --- Probiotic Antimicrobial Factors --- p.25 / Chapter 1.3.3.4 --- Epithelial Adherence --- p.27 / Chapter 1.3.4 --- Recent Findings in Ulcerative Colitis Treatment --- p.28 / Chapter 1.4 --- Lactococcus lactis --- p.29 / Chapter 1.4.1 --- Overview --- p.29 / Chapter 1.4.2 --- Gene Expression System --- p.30 / Chapter 1.4.3 --- Nisin-Inducible Controlled Gene Expression (NICE) System --- p.31 / Chapter 1.4.4 --- Recent Studies of Treating Ulcerative Colitis with L. lactis and Recombinant L. lactis --- p.32 / Chapter 1.4.5 --- Safety Concern of the Use of Probiotics and Transgenic Probiotics --- p.33 / Chapter 1.5 --- Aims --- p.35 / Chapter Chapter 2 --- Material and Methodology --- p.36 / Chapter 2.1 --- General Materials --- p.36 / Chapter 2.1.1 --- Chemicals --- p.36 / Chapter 2.1.2 --- Antibodies and Commercial Kits --- p.41 / Chapter 2.1.3 --- Bacteria --- p.43 / Chapter 2.1.4 --- Animals --- p.43 / Chapter 2.1.5 --- Cell Lines --- p.44 / Chapter 2.1.5.1 --- Mouse Colonic Epithelial Cells --- p.44 / Chapter 2.1.5.2 --- Mouse Macrophages --- p.44 / Chapter 2.2 --- Experimental Designs --- p.45 / Chapter 2.2.1 --- Construction of mCRAMP-Encoding Lactococcus lactis --- p.45 / Chapter 2.2.1.1 --- Enumeration of L. lactis --- p.45 / Chapter 2.2.1.2 --- Bacteriostatic Effect of mCRAMP on L. lactis --- p.46 / Chapter 2.2.1.3 --- Construction of mCRAMP-Encoding L. lactis --- p.46 / Chapter 2.2.1.4 --- Detection of mCRAMP Production by Western Immunoblotting --- p.50 / Chapter 2.2.2 --- In vivo Studies --- p.52 / Chapter 2.2.2.1 --- Survival of mCRAMP-Encoding L. lactis in Murine Colon --- p.52 / Chapter 2.2.2.2 --- Toxicity of mCRAMP-Encoding L. lactis --- p.53 / Chapter 2.2.2.3 --- Determination of mCRAMP Expression in Colon Tissue --- p.53 / Chapter 2.2.2.4 --- Induction of Colitis --- p.54 / Chapter 2.2.2.5 --- Probiotic and Sulfasalazine Treatment --- p.54 / Chapter 2.2.2.6 --- Clinical Symptoms --- p.56 / Chapter 2.2.2.7 --- Morphological Analysis --- p.56 / Chapter 2.2.2.7.1 --- Haematoxylin-Eosin (H&E) Staining --- p.56 / Chapter 2.2.2.7.2 --- Periodic Acid-Schiff (PAS) Staining --- p.58 / Chapter 2.2.2.8 --- Assessment of Apoptosis and Proliferation by Immunohistochemistry --- p.60 / Chapter 2.2.2.8.1 --- Determination of Cell Apoptosis by Terminal Deoxynucleotidyl Transferase dUTP Nick-end Labeling --- p.60 / Chapter 2.2.2.8.2 --- Determination of Cell Proliferation by Proliferating Cell Nuclear Antigen (PCNA) Staining --- p.61 / Chapter 2.2.2.9 --- Determination of the Degree of Inflammation --- p.63 / Chapter 2.2.2.9.1 --- Colonic Myeloperoxidase (MPO) Activity --- p.63 / Chapter 2.2.2.9.2 --- Colonic Malondialdehyde (MDA) Level --- p.63 / Chapter 2.2.2.10 --- Fecal Microbiota Count --- p.64 / Chapter 2.2.2.11 --- mRNA Expression of Inflammatory Cytokines --- p.64 / Chapter 2.2.3 --- In vitro Studies --- p.66 / Chapter 2.2.3.1 --- Determination of Anti-inflammatory Effects of mCRAMP --- p.66 / Chapter 2.2.3.1.1 --- Cell Viability --- p.66 / Chapter 2.2.3.1.2 --- Determination of TNF-α Secretion under Stimulation of LTA and LPS --- p.66 / Chapter 2.2.3.1.3 --- Effects of mCRAMP on TNF-α Secretion Under Stimulation of LTA or LPS --- p.67 / Chapter 2.2.3.1.4 --- Effects of Pertussis Toxin (PTX) on the Inhibition of TNF-α Secretion by mCRAMP --- p.67 / Chapter 2.2.3.1.5 --- Nuclear Factor-κB (NF-κB) Luciferase Reporter Gene Assay in RAW 264.7 cells --- p.68 / Chapter 2.2.3.1.6 --- Determination of IκBα Expression and Phosphorylation by Western Immunoblotting --- p.69 / Chapter 2.2.3.1.7 --- Determination of Inducible Nitric Oxide Synthases (iNOS) and Cyclooxygenase-2 (COX-2) Expression by Western Immunoblotting --- p.70 / Chapter 2.2.3.2 --- Determination of Wound Healing Effects of mCRAMP --- p.72 / Chapter 2.2.3.2.1 --- Cell Viability --- p.72 / Chapter 2.2.3.2.2 --- Cell Migration --- p.74 / Chapter 2.2.3.2.3 --- Determination of Epidermal Growth Factor Receptor (EGFR), Extracellular Signal-Regulated Protein Kinase (ERK1/2) and p38 Expression and Phosphorylation by Western Immunoblotting --- p.76 / Chapter 2.3 --- Statistical Analysis --- p.76 / Chapter Chapter 3 --- Result --- p.77 / Chapter 3.1 --- Protective Effects of Cathelicidin-Encoding Lactococcus lactis in Murine Ulcerative Colitis --- p.77 / Chapter 3.1.1 --- Introduction --- p.77 / Chapter 3.1.2 --- Results --- p.79 / Chapter 3.1.2.1 --- Survival of mCRAMP-Encoding L. latis in Murine Colon --- p.79 / Chapter 3.1.2.2 --- Detection of mCRAMP-Encoded by L. lactis in vivo --- p.81 / Chapter 3.1.2.3 --- Toxicity of mCRAMP-Encoding L. lactis --- p.84 / Chapter 3.1.2.4 --- Clinical Symptoms --- p.86 / Chapter 3.1.2.5 --- Histology Evaluation --- p.89 / Chapter 3.1.2.6 --- Apoptosis --- p.93 / Chapter 3.1.2.7 --- Determination of mCRAMP Expression in Colon Tissue --- p.96 / Chapter 3.1.2.8 --- Determination of the Degree of Inflammation --- p.101 / Chapter 3.1.2.9 --- Faecal Microbiota Populations --- p.105 / Chapter 3.1.3 --- Discussion --- p.108 / Chapter 3.2 --- Therapeutic Effects of Cathelicidin-Encoding Lactococcus lactis in Murine Ulcerative Colitis --- p.113 / Chapter 3.2.1 --- Introduction --- p.113 / Chapter 3.2.2 --- Results --- p.115 / Chapter 3.2.2.1 --- Clinical Symptoms --- p.115 / Chapter 3.2.2.2 --- Histology Evaluation --- p.117 / Chapter 3.2.2.3 --- Cell Death and Proliferation in Colitis --- p.123 / Chapter 3.2.2.4 --- Determination of mCRAMP Expression in Colon Tissues --- p.127 / Chapter 3.2.2.5 --- Determination of the Degree of Inflammation --- p.130 / Chapter 3.2.2.6 --- Faecal Microbiota Populations --- p.133 / Chapter 3.2.3 --- Discussion --- p.135 / Chapter 3.3 --- Mechanistic Study of the Anti-inflammatory Effects of mCRAMP in Mouse Macrophages --- p.139 / Chapter 3.3.1 --- Introduction --- p.139 / Chapter 3.3.2 --- Results --- p.145 / Chapter 3.3.2.1 --- Viability of Macrophages --- p.145 / Chapter 3.3.2.2 --- Effects of LTA and LPS on Tumour Necrosis Factor-α (TNF-α) Release from Macrophages --- p.150 / Chapter 3.3.2.3 --- The Inhibition of TNF-α Secretion by mCRAMP --- p.153 / Chapter 3.3.2.4 --- Inhibition of TNF-α Secretion by mCRAMP Independent to GPCR Stimulation --- p.158 / Chapter 3.3.2.5 --- Activation of NF-κB Through Detection of Luciferase Activity --- p.163 / Chapter 3.3.2.6 --- Determination of the Expression and Phosphorylation of IκBα by Western Immunoblotting --- p.166 / Chapter 3.3.2.7 --- Determination of iNOS and COX-2 Expression by Western Immunoblotting --- p.169 / Chapter 3.3.2.8 --- The Suppression of iNOS and COX-2 Expression by mCRAMP was Independent to GPCR and P2X₇ Signalling --- p.183 / Chapter 3.3.3 --- Discussion --- p.188 / Chapter 3.4 --- Mechanistic Study on Wound Healing Effect of mCRAMP in Mouse Colon Epithelial Cells --- p.193 / Chapter 3.4.1 --- Introduction --- p.193 / Chapter 3.4.2 --- Results --- p.196 / Chapter 3.4.2.1 --- Cell Viability --- p.196 / Chapter 3.4.2.1.1 --- MTT Assay --- p.196 / Chapter 3.4.2.1.2 --- BrdU Incorporation --- p.200 / Chapter 3.4.2.2 --- Cell Migration --- p.202 / Chapter 3.4.2.3 --- Determination of Epidermal Growth Factor Receptor (EGFR), Extracellular Signal-Regulated Protein Kinase (ERK1/2) and p38 Expression and Phosphorylation by Western Immunoblotting --- p.210 / Chapter 3.4.3 --- Discussion --- p.215 / Chapter 4 Discussion and Future Perspectives --- p.219 / Publications --- p.224 / References --- p.227

A large amount of cheese is lost every year due to mold contamination. Biopreservation, which is the use of biological entities (microbes) and their metabolites to suppress microbial spoilage instead of chemical preservatives has lately gained increasing interest. Lactic acid bacteria (LAB) have the potential for use in biopreservation, because they are safe to consume and naturally exist in many foods. In this study, fifteen strains of lactobacilli isolated from dairy products, vegetables, and fermented pickles were tested by agar overlay assay for their anti-mold activity. Six strains grown on MRS agar showed strong inhibitory activity against a target mold (Penicillium sp. at 105 spores/ml) isolated from the surface of Cheddar cheese. The isolates were identified by biochemical tests using API CHL50 strips. Five strains were identified as Lactobacillus plantarum, and one strain as Pediococcus pentasaceus. Well-diffusion method was used to demonstrate anti-mold activity in concentrated cell-free supernatants. Supernatants from all strains showed inhibition of the target mold (indicator). The anti-mold compound(s) produced by all the strains was heat-resistant (100o C for 15 min). Supernatants from 5 strains retained the anti-mold activity when the pH was adjusted to 6.8 ± 0.2, while one strain DC2 isolated from cheese lost its anti-mold activity at that pH. Temperature of incubation of cultures affected anti-mold activity. The optimum was 37o C. Very little or no inhibition was noted when cultures were incubated at either 10 or 55 °C. A preliminary study of applying anti-mold lactobacilli in Cheddar cheese was completed. Anti-mold LAB was added to the cheese milk as an adjunct to give 105 cfu/ml. After 1-week and 1-month ripening, mold (10~20spores) was added on to the surface, and the cheese was wrapped loosely. The appearance of the mold on cheese surface was monitored. Mold was not present on the 1-week old cheese “NB in milk” until the 6th day after the control cheese (made without strain NB) showed signs of mold. The 1-month old cheese “NB in milk ” extended the shelf life 17 days longer than the control cheese.

Lactobacillus plantarum and subspecies of Lactobacillus casei were isolated from good quality mature Cheddar cheese and characterized with respect to metabolic functions that would allow their use in cheesemaking. In this way microbiological control of the maturation process with particular emphasis on protein catabolism was achieved. The lactobacilli isolated were selected for low growth rates (and acid production) in milk, and low proteinase activity to allow for their addition in high numbers to cheesemilk together with the normal starter flora (group N streptococci). The growth and acid production of the starter bacteria were unaffected by the presence of the lactobacilli during cheese manufacture and it was found that the added lactobacilli were able to grow and function under the conditions prevalent in Cheddar cheese during maturation. It was also demonstrated that the lactobacilli could be grown in an artificial medium to high numbers under controlled conditions and could be harvested for the preparation of cell concentrates, a necessary characteristic for commercialization. The lactobacilli also metabolized citrate, a potential problem in cheese maturation associated with C02 production but this did not adversely affect the maturation process under the conditions used. Compared to the group N streptococci the non-starter lactobacilli possessed a proteinase system that had a higher temperature optimum and was less affected by heat and sodium chloride. They also possessed a more active peptidase system although both the lactobacilli and the starter organisms possessed a similar range of peptidases. Non-starter lactobacilli were added to normal cheese and cheese made with proteinase negative starter. The added organisms did not adversely affect manufacturing parameters and did not metabolize citrate or lead to the formation of biogenic amines. However protein catabolism rates, particularly with respect to peptide degradation, were increased, as was flavour development and intensity. It was observed that the body and texture of the cheeses was unaffected by the treatment. By controlling both the starter and non-starter microflora in the cheeses a practical system for favourably influencing cheese maturation was possible. The investigation has demonstrated that carefully selected and characterized non-starter lactobacilli can be incorporated into Cheddar cheese manufacture in order to influence flavour development during maturation. Moreover the organisms can be added to the vat stage of manufacture without causing problems to the manufacturing process. This approach is a simple cost effective means of improving the cost of Cheddar cheese production and provides an unique opportunity to improve and control quality of all Cheddar cheese produced.

Graduation date: 1995

Graduation date: 1994

Graduation date: 1994

Carnocyclin A (CclA) is a remarkably stable, potent bacteriocin produced by Carnobacterium maltaromaticum UAL307. Elucidation of the amino acid and genetic sequences revealed that CclA is a circular bacteriocin. Preliminary structural studies (dynamic light scattering, NMR, circular dichroism, stereochemical analysis) indicated that CclA is monomeric and alpha-helical in aqueous conditions and composed of L-residues. The 3D structure of [13C,15N]CclA was solved by NMR, revealing a compact arrangement of four helices. To examine the structure of the precursor peptide (pCclA) several fusion proteins were constructed and overexpressed; however, pCclA could not be isolated. To investigate the requirements for cyclization, several internally hexahistidine-tagged (His6) pCclA mutants were constructed. Expression conditions are underway. PisI was heterologously expressed and confirmed to impart protection against piscicolin 126 (PisA). Labeled and unlabeled PisA and PisI were purified following overexpression as maltose-binding protein fusions (MalE-fusions) and Factor Xa cleavage. NMR studies indicated that PisI and PisA do not physically interact. The 3D structure of PisI was solved by NMR, confirming that the four-helix bundle is a conserved motif for the immunity proteins of type IIa bacteriocins. The putative receptor proteins for these bacteriocins were cloned and overexpressed as His6-fusion proteins. Experiments are underway to optimize the expression and purification of these membrane proteins. The peptidase domain of the ABC-transporter protein (CbnTP) for carnobacteriocin B2 (CbnB2) was overexpressed as a His6-fusion protein. Active protease could not be purified from inclusion bodies, but was obtained as soluble protein following low-temperature overexpression. The CbnB2 precursor pCbnB2 (and a truncated derivative pCbnB2-RP) was purified following overexpression as a MalE-fusion and Factor Xa cleavage. pCbnB2 was incubated with CbnTP and MALDI-TOF and activity testing confirmed that CbnTP cleaved the leader peptide from pCbnB2. Five CysSer CbnTP mutants were constructed. Crystallographic studies of CbnTP are underway. Six bacteriocins (nisin, gallidermin, lacticin 3147, CclA, PisA, enterocin 710C) were tested against Gram-negative bacteria (E. coli DH5, Pseudomonas aeruginosa ATCC 14207, Salmonella typhimurium ATCC 23564) in the absence and presence of EDTA. PisA and lacticin 3147 exhibited minimal activity, whereas the other bacteriocins killed at least one strain, in the presence of EDTA.

The work presented in this thesis is concerned with the effect of several antibiotics and quaternary ammonium sanitizers upon growth of lactic acid bacteria. Section I reports the purification of beta-lactamase from Lactococcus cremoris PR-108, by ion exchange chromatography, using the chromogenic substrate pyridine-2-azo-p-dimethylaniline (PADAC) as the enzymatic indicator. Section II reports a study of the influence of antibiotics on lactococcal growth, where the effects of incubation time, culture dilution and the use of seeded and spread agar plate techniques are investigated. These studies were extended, in section III, to include investigations of the effect of quaternary ammonium base sanitizer (Ster-bac) on lactic starters. In addition, this section describes an reverse phase high performance liquid chromatography assay for the detection of quaternary ammonium compounds in milk. / Graduation date: 1991

Immunomodulatory effects of lactic acid bacteria vary with strain and may vary with growth phase and medium. The ability of different lactobacilli strains (Lactobacillus helveticus R0052, L. rhamnosus R0011, L. rhamnosus GG) at different growth phases to modulate macrophage and intestinal epithelial cell cytokine production following a pro-inflammatory challenge was examined. Modulation of cytokine production by human macrophage cell lines (U-937) and intestinal epithelial cells (HT-29) induced by Tumor Necrosis Factor α was assayed by ELISA for interleukin-8 (IL-8). Granulocyte-macrophage colony stimulating factor (GM-CSF) production was assayed by ELISA in the HT-29 cell line. Strain-dependent differences were observed in the ability of viable bacteria and spent de Mann-Rogosa- Sharpe (MRS) broths from log versus stationary growth phase in HT-29 and U-937 cells. Overall, variation in the immunomodulatory activity of these lactic acid bacteria and spent broths reflects not only strain variation but potentially also differences in growth phase and substrate. / UOIT

Lactic acid, which induces pH depression, leads to ATP efflux from muscle to extracellular space: it was reported that CFTR was involved in this process. However, the mechanism by which lactic acid activated CFTR and brought about the ATP release is still unknown. This study was performed to investigate (1) what channels may be involved or even conduct ATP release, and (2) how lactic acid activated CFTR. Expression of the possible channels that may conduct ATP release in L6 cells was investigated using RT-PCR: ClC-2, ClC-3, ClC-7, CACC, VDAC, connexin 40, connexin 43 and pannexin 3 were expressed in L6. Incubation of cultured L6 cells with lactic acid (10 mM) increased the extracellular ATP from 0.6 ± 0.06 to 1.1 ± 0.09 nM (P ? 0.05), indicating that lactic acid stimulated ATP efflux in vitro. The non-specific chloride channel inhibitor, DIDS, failed to abolish the lactic-acid-induced ATP release, suggesting that DIDS-sensitive chloride channels were not involved in the ATP efflux. Among the non-specific inhibitors of connexin channels, gadolinium inhibited acidosis-induced ATP efflux, but carbenoxolone failed to inhibit it, and so the role of connexins remains uncertain. The specific inhibitor of CFTR, CFTRinh-172, and the non-specific open-channel blocker of CFTR, glibenclamide, both abolished the acidosis-induced ATP release, but another specific inhibitor of CFTR, GlyH-101, which blocks CFTR from the external side, failed to abolish the ATP release, suggesting that acidosis-induced ATP is dependent on CFTR-activation, but does not involve ATP moving through the CFTR chloride channel. We hypothesize that, at low pH, the Na+/H+ exchanger (NHX) extruded H+ out of the cell and the resulting intracellular Na+ was transported out by Ca2+/Na+ exchanger (NCX); the localized increase in Ca2+ activated adenyl cyclase (AC), thus elevating intracellular cAMP; cAMP-activated-PKA then phosphorylated CFTR, which regulated an ATP release channel. KT-5720, an inhibitor of PKA, abolished the acidosis-induced ATP release, and forskolin, an agent that elevates cAMP, stimulated it, suggesting that the cAMP/PKA pathway was involved. The specific inhibitor of NCX, SN-6 and KB-R7943, both abolished the acidosis-induced ATP release, supporting a role for NCX in mediating this process. However, amiloride, the non-specific inhibitor of NHX failed to abolish ATP efflux. The whole cell Cl- currents were studied in L6 cells: lactic acid increased the whole cell currents from 2.33 ± 0.10 to 3.54 ± 0.34 nA (P ? 0.05), and this lactic-acid-induced increase in Cl- current could be inhibited by CFTRinh-172, suggesting that the CFTR Cl- channel was opened at low pH. Moreover, forskolin increased whole cell Cl- currents, which supported a role for the cAMP/PKA pathway in the lactic-acid-induced increase in CFTR current. These data confirm that CFTR is involved in the lactic-acid-induced ATP release from L6 cells. The roles of the NCX and cAMP/PKA pathway in activating CFTR at low pH are supported, but further studies are required to determine whether the NHX is involved in CFTR activation and whether connexins participate in ATP release. / published_or_final_version / Physiology / Master / Master of Philosophy