Benders'dictionary of nutrition and food technology

46shape: spherical (coccus); rodlike (bacilli); spiral (spirillum);comma-shaped (vibrio); corkscrew-shaped (spirochaetes) orfilamentous.Other classifications are based on whether or not they arestained by Gram stain, aerobic or anaerobic, and autotrophic(see autotrophes) or heterotrophic.Some bacteria form spores, which are relatively resistant toheat and sterilising agents. Bacteria are responsible for muchfood spoilage, and for disease (pathogenic bacteria that producetoxins), but they are also made use of, for example in the picklingprocess and fermentation of milk, as well as in the manufactureof vitamins and amino acids and a variety of enzymesand hormones.Between 45 and 85% of the dry matter of bacteria is protein,and some can be grown on petroleum residues, methane ormethanol, for use in animal feed.bacterial count See plate count.bacterial filter A filter 0.5–5 µm in diameter (fine enough toprevent the passage of bacteria); permits removal of bacteriaand hence sterilisation of solutions. Viruses are considerablysmaller, and will pass through a bacterial filter.bactericidal Conditions or compounds that are capable of killingbacteria.See also bacteriostatic.bacteriocins Antibiotic peptides produced by lactic acid bacteriaand some other micro-organisms to inhibit the growth of others.See also probiotics.bacteriophage Viruses that attack bacteria, commonly known asphages. They pass through bacterial filters, and can be a causeof considerable trouble in bacterial cultures (e.g. milk starter cultures).Each phage acts specifically against a particular species ofbacterium; this can be exploited in phage typing as a means ofidentifying bacteria.bacteriostatic Conditions or compounds that are capable ofinhibiting growth of bacteria, but are not bactericidal.Bacterium aceti See ACETOBACTER.Bactofoss TM See bioluminescence.bactofugation Belgian process for removing bacteria from milkusing a high-speed centrifuge.bactometer A device for the rapid estimation of bacterial contamination(within a few hours) based on measuring the earlystages of breakdown of nutrients by the bacteria throughchanges in the electrical impedance of the medium.Bactoscan TM See deft.