LAB 5 SHAHRUL EZZATI SHAHRUL AMIR -111416-

INTRODUCTION
Multiwavelength ultraviolet/visible (Uv-vis) spectroscopy is a versatile,quantitative, rapid, and reliable analytical tool that has immediate applications as a biosensor for the detection, identification, and enumeration of microorganisms and cells. The sample information contained in a spectrum includes cell size, chemical composition, shape, and information on their internal structure.  This information is obtained from the spectroscopic analysis of a sample measured over a broad range of wavelengths (200-900 nm) and/or with the scattered light measured at one or many different angles. The potential to extract  large amounts of information from a single multiwavelength measurement makes Uv-vis spectroscopy a powerful characterization tool. In addition, process Uv-vis spectrometers and miniaturized systems, make this technique readily available for real-time in situ monitoring of biological, and environmental processes.

Bacteriocins comprise a large and diverse group of ribosomally synthesised antimicrobial proteins or peptides. Although bacteriocins can be found in numerous Gram-positive and Gram-negative bacteria, those produced by lactic acid bacteria (LAB) have receive special attention in recent years due to their poential application in the food industry as natural biopreservatives. Different classes of LAB bacteriocin have been identified on the basis of biochemical and genetic characterization.

OBJECTIVE
To determine the antimicrobial effects of extracellular extracts of selected LAB strains.

RESULTS

PART 1 : Determination of bacteriocin activity via agar diffusion test

STRAINS LAB	Strains of spoilage / pathogenic bacteria	Inhibitio zone ( cm )
L.plantanum	S.aureus	0.0
	K.pneumonia	0.9
	P.aeruginose	0.9
L.casei	S.aureus	0.0
	K.pneumonia	0.7
	P.aeruginose	0.7
L.brevis	S.aureus	0.0
	K.pneumonia	0.6
	P.aeruginose	0.7

LAB : L.plantanum

K.pneumonia

P.aeruginosa

S.aureus

LAB : L.casei

K.pneumonia

P.aeruginosa

S.aureus

LAB : L.brevis

K.pneumonia

P.aeruginosa

S.aureus

PART II :Determination of bacteriocin activity via optical density

Dilutions	OD600 of spoilage/pathogenic bacteria
	S.aureus	K.pneumonia	P.aeruginosa
0X	-	-	-
2X	0.454	0.484	0.410
10X	0.610	0.696	0.620
50X	0.386	0.571	0.312
100X	0.238	0.464	0.265
Equation	y = 0.013x+0.278	y = 0.113x+0.111	y = -0.031x+0.532
OD600  of control	0.270	0.892	0.432
50% of OD600	0.135	0.446	0.216
AU/ml	-11	2.96	10.19

DISCUSSION
Multiwavelength Uv-vis spectra of microorganisms and cell suspensions contain quantitative information on their properties such as number, size, shape, chemical composition, and internal structure. These properties are essential for the identification and classification of cells.  The complexity of microorganisms in terms of their chemical composition and internal structure make the interpretation of their spectral signature a difficult task. In this lab report  proposed for the interpretation of the multiwavelength spectra of microorganisms.
The optical properties as functions of wavelength, and available literature data on the size and chemical composition of E. coli cells and S. aureus have been used to explore the sensitivity of the calculated spectra to the model parameters. It is shown that the proposed model can reproduce the features of experimentally measured spectra. The sensitivity of the spectra to the model parameters suggests that the proposed model can be used for the quantitative deconvolution of the Uv-vis spectra in terms of critical information necessary for the detection and identification of microorganisms.
An anti-microbial is a substance that kills or inhibits the growth of microorganisms such as bacteria, fungi, or protozoans. Antimicrobial drugs either kill microbes (microbiocidal) or prevent the growth of microbes (microbiostatic). Disinfectants are antimicrobial substances used on non-living objects or outside the body.
A drug used to treat a microbial infection. "Antimicrobial" is a general term that refers to a group of drugs that includes antibiotics, antifungals, antiprotozoals, and antivirals.

CONCLUSION
A model for the interpretation of the multiwavelength Uv-vis spectra of microorganisms and cells has been formulated. The proposed interpretation model is based on light scattering theory, spectral deconvolution techniques, and on the approximation of the frequency dependent optical properties of the basic constituents of living organisms.